Annan, Noel. Changing enemies: The defeat and regeneration of Germany. HarperCollins, London - November 1995.
Noel Annan was a young cadet in the British Intelligence Division known as M.I.14 responsible for monitoring German messages during World War II. His work put him in close proximity to leading figures in the British military as well as such secret resources as the British decoder called "Ultra." From this prime perch Annan witnessed the operations of England's war effort.

Bertrand, Gustave. Enigma ou la plus grande enigme de la guerre 1939-1945. Librairie Plon, Paris - 1973.

Brown, Anthony Cave. Body guards of lies. Harper & Row Publishers, San Francisco - 1975.
Account on WS’s interests: p.168 (Churchill told Kleist of the Schwarze Kapelle in 1938: “You can have everything, but first bring us Hitler’s head”), p.186-191 (The Venlo incident), 226-27 (Canaris’s tears for Heydrich and “almost feminine sensibility made him [WS] as moody as a film star no longer sure of success”), p.310 (Goerdeler had prepared a Memorendum at Wallenberg’s request, on the Schwarze Kapelle’s intentions for transmission to Churchill… did not receive a reply), p. 349 (jugement of Helmut Knochen the head of Gestapo in France who had been with WS at Venlo) p.387-8 (Stalin seriously suggested in Teheran, that after the war 50,00 officers of the German army should be “rounded up and shot”: had he learned the Thukachevsky lesson? This confirmed Churchill that he would never have any agreement by his two allies to a deal with the Schwarze Kapelle) p.446 (Operation Zeppelin), p.455-457 (WS’s infiltration of the Schwarze Kapelle in 1943 with the help of De Crinis, which induced the Vermaeren in Turkey to defect to the British), p. 769 (Churchill later agreed that his refusal to in negotiate with the Schwarze Kapelle had been wrong), p.816 (Knochen executed by the French, end of Schellenberg without details). Without reducing the exceptional value of Ultra, it is difficult to follow Anthony Cave-Brown who presents it as the universal British “deus ex machina.”

Budiansky Stephen. Battle of Wits: The Complete Story of Codebreaking in World War II. Free Press October, 2000
Stephen Budiansky, who knows both math and military history, has provided us with a well written new telling of the story of how the USA and UK cracked German and Japanese codes, and used this knowledge in winning World War II. This is the best treatment for a wide audience since David Kahn's The Codebreakers, and contains much new material from documents declassified in the last decade. Budiansky is particularly good at explaining how the cryptanalysts actually worked, with excellent diagrams. He also explains how the early data-processing machines they used functioned--at the dawn of the computer era. As for the war itself, he sticks to the high points, such as Midway and the Battle of the Atlantic, but the military history is accurate.

Calvocoressi P. Top Secret Ultra, Cassell, London - 1980.

Flannery, Sarah. In code: A mathematical journey. Workman Publishing Company, New York - 2001.
This is the book enabling normal human beings to understand how Ultra decoded ciphers during World War II

Garlinski Josef: Intercept. Secrets of the Enigma War. J.M.Dent & Sons Ltd. London, Melbourne, Toronto, 1979.

Hinsley F. H., Stripp Alan Codebreakers: The Inside Story of Bletchley Park Oxford University Press, Oxford (U.K.) - July, 2001
When the gag order was finally lifted circa 1970 on the Bletchley Park operations, a lot of scientific, historical, and technical histories appeared. And there was a great hue and cry among military and political historians that the whole history of the British and American war against Hitler’s Germany would have to be rewritten. Well, much of that has been proven to be just hyperbole but it is generally agreed that the war was shortened by about two years. But the closer the Allies got to Germany the less role Bletchley played for the German forces used landlines for most strategic communications from mid 1944 on. Also they had another machine known as FISH which was not as easily read as Enigma. This book is a collection of personal narratives of life at Bletchley and how tedious most of the work there was, no matter how essential. Harry Hinsley, one of the authors, was a "whiz kid" recruited directly from university and after the war became a professor without ever completing his studies. Over the years he has written the monumental multivolume official history of British intelligence operations in WW II and many historical papers. Alan Stripp, was one of the original operatives and served for many years.

Hodges, Andrew. Hofstadter, Douglas. Alan Turing: The Enigma of Intelligence. Simon and Schuster, New York - 1983.
With loving care, Hodges follows Turing's life from the clumsy child whose largely absentee parents were caught up in maintaining the British imperial presence in India, to the mathematically precocious adolescent facing teachers for whom mathematics imparted a bad smell to a room, finally coming into his own at Cambridge University where he wrote the paper that provided the conceptual underpinnings of the all-purpose computers we all use today. Hodges carefully explains Turing's crucial contributions to breaking the secret codes that the German military used all through the Second World War, confident in the security provided by their "Enigma" machines. Turing's highly successful war-time practical work known only to a few, his efforts after the war to enable the construction of a general purpose electronic computer were frustrated by bureaucratic mismanagement and by a lack of appreciation of the value of his ideas, many of which came to birth much later. A burglary of his house that a prudent man would have kept to himself, led to Turing's homosexuality getting public when he reported the crime to the police. He was prosecuted for "gross indecency" and sentenced to a course of injections of estrogen intended to diminish his sex drive. We will never know how much this barbaric treatment contributed to his suicide or what he might have accomplished had his life not been cut short. This man should have been prized as a world national hero.
Hughes-Wilson John. Military intelligence Blunders Carroll & Graf Publishers, New York - 1999.
I'm not sure the title of this book is a very good description of what it addresses, though military intelligence activities (both in true intelligence work, but also quite a bit of counter-intelligence stuff) are discussed.
Even if one read dozens of books discussing the conflicts covered here (five chapters of various aspects of World War II and then one each on Vietnam, '73 Arab-Israeli War, Falklands War, Gulf War) there is quite a bit of new material and insight here. In addition to intelligence work, he covers political, military, and diplomatic activities that have substantial impacts on the campaigns discussed.
This book fills a real gap, in my estimation, in understanding much that is scarcely reported and seldom discussed about why wars and battles go the way they do. Overall a very good assessment of intel activities and the pol-mil considerations that go into why a particular campaign was successful or not (at least at the outset).

Jones R.V. Most secret war Hamish Hamilton, London - 1978.
The author as a relatively young man was the technical intelligence director for the British Royal Air Force in WW II. As such he was involved in the development of active, passive, and counter measures to thwart the German Luftwaffe.
Developments included radars, anti ship missiles, jet engines, defense against buzz bombs, and the jamming of radio navigation systems used by the Germans.
After the war the author returned to Scotland to become a university professor. He returned to service during the Korean War period. His other book Reflections on Intelligence reveals him to be a man of erudition and covers and fills in some of the gaps in the story told herein which could not be revealed at the time this book was written.

Kahn David. The Codebreakers, Sphere Books, London - 1973.
Account s on WS p.449, 450, 452

Kahn, David: Seizing the Enigma The race to break the German U-boats code, 1939-1943 . Arrow Books Ltd, London - 1991.
In 1941, the Battle of Britain is intensifying. The Kriegsmarine submarines, organized in groups - wolf packs - were cutting the life-line the British defense depended on - the convoys which supply Britain with food, military supplies and raw materials. And the U-Bot got pretty much successful in it, sinking more ships each month than Britain and United States could build. Meanwhile, the group of mathematicians, linguists and other odd characters located a top-secret base in Bletchley Park, Buckinghamshire, was trying in frenzy to decode the German naval code, Enigma... David Kahn has produced a very well researched and clearly written book on this segment of naval history, which has long remained classified. The story of Enigma is traced from the Arthur Scherbius's design, through the first successful decoding made by Marian Rejewski's group in Poland, and finally to Alan Turing and the Hut 8 staff in Bletchley Park. We learn that while direct attack on the cipher was mindbogglingly impossible, the chances for decoding being 150 million million million to one, the Brits had to find bypasses, raiding German boats for the on-board code books, employing "kisses" (identical messages transmitted in two different cryptosystems), and finally mechanising the solution finding with the "bombes".
The emphasis of the book is more on the naval war than on the cryptology. Although the operation of Enigma machine is described to some extent, you will not be able to fully understand its workings from it alone. Singh's Code Book, for instance, has a much better introduction to it. It also limits its scope quite narrowly, not spending one single word on the fact that while Hut 8 was busy solving naval Enigma, some hundred yards away the world's first electronic computer - Colossus - was built in attempt to solve the German Lorenz cipher.
The book comes with an exhaustive list of notes, an excellent bibliography and a useful index.

Kozaczuk. W.: Enigma. How the German Machine Cipher Was Broken, and How it Was Read by the Allies in World War Two. Arms and Armour Press. London, Melbourne, Cape Town - 1984.
This book tells the story of the Polish breaking of the German Enigma code before WWII and thru the early part of the war. The famous English Enigma work was based on the earlier work performed by 3 Polish mathematicians. This book tells how the Polish broke the code using mathematics (not a captured machine as is commonly thought) and details the methods used to decrypt messages when settings were changed. There is a lot of (Polish) patriotic pride in this book, which occasionally gets in the way of the content, but it is an excellent book nonetheless. It includes an appendix in which the mathematician who originally broke Enigma explains exactly how he did it which is especially interesting.

Lewin, Ronald. Ultra Goes to War: The Secret Story. Book Club Associates, London - 1978.

Montagu E. Beyond Top Secret Ultra, Coward McCann & Geoghegan, New York - 1978, copy 1977.

Parrish Thomas. The Ultra Americans: the U.S. Role in Breaking the Nazi Codes. Stein and Day, New York - 1986.

Sebag-Montefiore, Hugh. Enigma: The Battle for the Code John Wiley & Sons, New York - 2000.
It's remarkable that 60 years on, new information continues to surface about the breaking of the Enigma code. Having followed much of the "new material" released over the last 20 years, it is great to see other key players in the Enigma drama getting due credit.
Forget about the attempts by Hollywood to credit the Americans with breaking the code, and find out in this book the huge contributions by the Poles (who were partly breaking Enigma in the early 1930's), the British and Canadian seaman (boarding subs and weather reporting trawlers to capture code books), and the French.
The book is not for those seeking a deep understanding of the deciphering techniques used at Bletchley Park - this is covered in other excellent volumes (see Sarah Flannery's book "In code: A mathematical journey" for a soft introduction to cryptography ). It does give detailed and personal accounts of the risks taken by others in the armed forces and outside to secure code books, Enigma machine wheels and other "cribs" to help the code breakers.
The sadest part is reading about the fate of the various Polish mathemeticians who pioneered the Enigma work throughout the 1930's, and who were mostly left to perish in tragic circumstances by the French and British, despite having been got out of Poland after the German invasion.

Polish American Journal The Enigma: the Secret Weapon of World War II', Polish American Journal - October 1990.

Rejewski, Marian. How Polish mathematicians deciphered Enigma. Annals Of the History of computing 3, No 3 – July 1981

Smith, Michael. Station X: decoding nazi secrets. TV Books Inc, New York - 1989.

Strong. Sir Kenneth. Men of intelligence. Cassell & Co, London - 1970.

Welchman Gordon The Hut Six Story. McGraw-Hill, New York - 1982.
The men and women of Bletchley Park, who repeatedly broke German military cyphers throughout the Second World War, made an important contribution to the allied success. This book, written by another one of the code-breakers provides a fascinating insight into the process.
Despite the core subject, this is not really a book about cryptography, but about how to manage people and technology to solve complex, important problems. Welchman was the "glue" between the pure ideas men like Alan Turing, and the code-breaking production line. His talents were clearly in building the organization, and liaising between the different parties so that interception, decoding, understanding and using the intelligence became a repeatable success.
Welchman's insights into British wartime society and bureaucracy are keen and frequently very humorous.
Although he was very modest about it, it is clear that Welchman was by no mean a cryptologist himself. The book does attempt to explain several of the ways in which Enigma was cracked, but the primarily verbal explanations are difficult to follow. However, this doesn't prevent an understanding of the principals, and how different methods were applied at different points during the war. See Sarah Flannery's book "In code: A mathematical journey" for a soft introduction to cryptography
The book does have some limitations. Because he was not personally involved, he explicitly refuses to discuss the effort focused on the German naval codes so important to the Battle of the Atlantic, and generally says little about the use of the intelligence information. Sadly, the current edition of the book omits much of Welchman's advice on the analysis of battlefield communications, and how to keep such communications secure. However, one observation has been retained - it was a fundamental mistake to believe Enigma was secure simply because of the enormous computing power required for a brute-force attack.

Winterbotham, Frederick William. The Ultra Secret. Weidenfeld & Nicholson, London - 1974.
In 1976 "A Man Called Intrepid" was a best seller in the US. In 1977 Frederick William Winterbotham published "The Ultra Secret", about the decryption of the German Enigma systems. In 1978 "Room 3603" was reprinted. They all are important books about WW2, altho "Room 3603" starts in the 1930s and has important information about intelligence activities.
This book tells about Winterbotham's involvement in solving the Enigma encryption system. A later book tells more of his personal history in the 1930s. Working for the Air Ministry, he travelled to Germany to sell aircraft parts, and met many high Nazi officials. He was such a good friend of Goering that he was the only foreigner allowed to fly his airplane thru the Third Reich! He was one of the top British Nazi sympathizers at the time, until 1937: he was summoned to the Berlin Foreign Office, and given 48 hours to leave the country, "or else". They finally discovered that Winterbotham really worked for Military Intelligence!

Woytak, Richard A. On the border of war and peace: Polish intelligence and diplomacy in 1937-1939 and the origins of the Ultra secret. Columbia University Press, New York - 1979.