I like book publishing contracts. I am very weird. They are a strange animal. Unique to the industry, hard for outsiders to understand. When I was at NYU, I took a course with Jan Constantine (General Counsel at the Authors Guild) and one of my favorite parts was learning about the cases that shaped the book contract as we know it.
I still have my notebook and folder from that class because I am a dork.
Anyway, back to the point. I was asked at a conference if there is a book to learn that sort of thing. And, yes, there are several. Jan used Negotiating the Book Contract by Mark Levine. (Mr. Levine also has a book for self-publishing authors called The Fine Print of Self Publishing which I'd recommend for all of you who DON'T want an agent.)
Sadly, I don't remember who asked me this originally.