What is Robin Williams favorite book?

There is no definitive answer to what Robin Williams' favorite book was. He was an avid reader with wide-ranging interests, so it's unlikely he had just one "favorite." He has, however, mentioned enjoying many books in interviews and public appearances. Some of the titles he has discussed include:

* "The Little Prince" by Antoine de Saint-Exupéry: He often cited this book as one that he enjoyed reading to his children.

* "The Hitchhiker's Guide to the Galaxy" by Douglas Adams: He was a fan of science fiction and humor, and this book fits both categories.

* "The Lord of the Rings" by J.R.R. Tolkien: He was known to have a fondness for fantasy and mythology.

* "The Catcher in the Rye" by J.D. Salinger: He has mentioned this book in interviews, indicating its influence on him.

It's impossible to definitively say which book was his absolute favorite, but these titles represent a range of his literary interests.