The most obvious one is David Hajdu's Positively Fourth Street, which chronicles the intertwined lives of Richard & Mini, Joan and Bob -- and Richard's first wife, Carolyn Hester shows up, as well. It's a year or so old, and should be pretty easily available through Amazon.com and the like, if not your local bookstore.

I disagree with some of the author's conclusions (but who am I?), though his research seems quite solid.