The List

"Audrey Hepburn" by Barry Paris -- The Best book on Audrey out there
"Audrey Style" by Pamela Keogh -- A vision into Audrey's personal style.
"Audrey" by Alexander Walker -- A solid bio.
"Audrey a Life in Pictures" by Carol Krenz -- A summarized book with loads of guess what? Yep! Pictures!
"Audrey Hepburn - An intiamte portrait" By Diana Maychick -- A Biography that caused controversy over the author claiming to know Audrey personally. Sean, Audrey's son, denies she did.

Also their are many good Audrey clubs on Yahoo such as Audrey's Place 2