The Art of Doubles by Pat Blaskower (1994, Paperback)

This is a great book on playing doubles. I've played tennis for 35-yrs. (since I was 7 y/o) and play mostly 4.0-4.5 singles, but play doubles on occassion and felt like I needed to brush up on my doubles skills. This book really helped my doubles game right away -- it made me better at poaching and playing the angles. I recommended my wife read this book as well (she has been playing for 2-3 years) and she also felt that it helped her game too. She plays mostly doubles and is a 3.0 player. My wife said that she needs to read it again because there was a lot of information for a new player to take in one reading.
My wife and I have been recommending this book to other players on our teams as an essential read if they want to play good doubles. Highly recommend this to anyone that needs help with their doubles game.