Good question. I looked at a lot of books. I wanted 1. good photos, 2. good technical info but still worded simply 3. good personal info about what chickens are like as pets. I ended up buying three books and I love and refer to them all.
1. Storey's Guide To Raising Chickens by Gail Damerow: I chose this because I read and trust the Storey's Guide books on various topics, and this book as a lot of "how to" stuff, giving me specs, and requirements, etc.
2. Living with Chickens by Jay Rossier. I chose this because it's a quality book with full color glossy photos and the text is double spaced and chopped into categories, so it is very easy to read and refer to rather than reading cover to cover.
3. Keep Chickens! by Barbara Kilarski. I chose this down to earth book because it focuses more on the pet aspect of keeping chickens, and it also focuses on small spaces and small flocks, which is what I wanted to do. This book is cute, offers good tips, and has interesting stories of their experiences with chickens, although still informative.
I find that when I refer to them, I grab all three from my book shelf. What one doesn't have, one of the other two will.
Hope that helps!