I don't have Cunningham's defend yourself books, but I do have his Gun Digest Book of the Revolver. It may still be too elementary for many of you folks, but I really like it. He doesn't really cover anything about fighting. It's a book about revolvers. There's really good pictorial essays on his universal revolver reload, as well as on his alternative competition reload. He has a separate essay for the left-handed reload. He covers malfunction clearances and has a really great little flowchart of what to do if you have problems. He's got a long chapter one one-handed reloading, again with really useful pictorial essays. Good tips on fit, customization, etc. Some of the info is a little outdated at this point, and a lot of it is basic, like how to clean a revolver. But the chapters on malfunctions and reloads, to me, made it very worthwhile.
I'd be very interested in hearing ideas about good revolver books. I've got a short list of revolver books I really liked. I'll put it down in case anyone's interested. It starts with Cunningham's.
Secrets of Double Action Shooting by Bob Nichols
Ed McGivern's Book of Fast and Fancy Revolver Shooting (not entirely what it sounds like--it has some really good stuff that's still very applicable)
Sixguns by Elmer Keith
I'm on the fence about Ed Lovett's The Snubby Revolver. I liked it, and found it interesting, but it's not really a book that goes into a great deal of detail about shooting snubbies. It's more a general kind of defensive living book with a few tips on revolvers, and arguments why they were such useful guns back in the day.
There are a few things available over at the Snub Gun Study Group page, including the book Snubby Chronicles.
http://snubgunstudygroup.com/downloads.html These are collections of articles of lesser or greater interest to various readers.
Apart from some interesting older stuff like Hatcher's Textbook of Pistols and Revolvers, or Tracy's The Service Revolver and How to Use it, which I consider largely of historical interest, I haven't come across a lot of other solid revolver material. DeBethencourt's little pamphlet 38 Straight Tips is good, but very brief. I hope his promised books show up someday!
Edit: I also really like Ayoob's Stressfire. Though that isn't specifically a revolver book, it does have a lot of revolver-focused stuff in it.