The first two chapters of my book,
SEALAB: America's Forgotten Quest to Live and Work on the Ocean Floor, give a good overview (in my opinion!) of the physics and physiology involved along with a history of diving (Chapter 1 is available
on my website and the first few pages of Chapter 2, which deals more with the history of diving, you can
see on Amazon, fyi.)
The most comprehensive history of diving is arguably
Deep Diving and Submarine Operations: A Manual for Deep Sea Divers and Compressed Air Workers, by Sir Robert Davis, now in a 9th edition. It's like a little encyclopedia of diving, filled with 600-plus pages of facts, illustrations and anecdotes and infused with some wry wit and humor. A much more concise but thorough history can be found in Robert C. Martin's
The Deep-Sea Diver: Yesterday, Today and Tomorrow. As someone else mentioned in this thread, the
U.S. Navy Diving Manual is a good source - well organized, clearly written and more readable than you might expect of a military "manual." And be sure to check out back issues of the Historical Diving Society USA's fine magazine, recently renamed
The Journal of Diving History. The special issue on Jacques Cousteau, for example, is well worth a read.
Also, an earlier Scubaboard thread that asked for "essential scuba related nonfiction" got a lot of good suggestions that someone compiled into a list within the thread, as you should be able to see here:
http://www.scubaboard.com/forums/book-media-reviews/443924-essential-scuba-related-nonfiction-3.html
Hope this info helps. . .