Every Pink Floyd fan should own "Saucerful of Secrets". It a fascinating book about this very private, secretive group. The writing is skillfully done, and it's a quick read. I used this book as the basis for an entire class I taught about Pink Floyd.
The book carries us through the history of the band from their births to the book's publication date in 1991. The early lives of the band members are interesting, but once the band is formed, it becomes fabulous. The book goes into great detail about the deterioration of Syd Barrett's mental state and how it affected the other members of the band. That's my favorite part of the book because I didn't know a lot of that. I was born in 1968 and came to Pink Floyd later. I always knew there was a guy named Syd in the band, but I had no idea how influential he was on everything the band has done since. It's great.
We also get a good look at much of the band's later work and the inspirations for it. I enjoyed reading about how the band evolved from a fringe, underground club band into one of the first super-groups playing stadiums. The book follows all the way through the break-up of the '70s/early '80s incarnation and their solo work. It also discusses the conflicts and court cases the former friends had following the break-up.
All in all, this is a great book. I recommend it to any Pink Floyd fan. I guarantee you'll learn something you probably didn't know about them.
Saucerful of Secrets: The Pink Floyd Odyssey