As luck would have it - I recently re-read the Dashiell Hammett book. It really holds up well as a good read. In the book Sam Spade is portrayed as a blonde Satan (not exactly picturing Bogart while reading it but that's OK since he's so great in the movie) and Brigid O'Shaughnessy was so beautiful men would kill or die for her (definitely not picturing Mary Astor when reading the book).
Interesting to note that Ward Bond probably became one of John Huston's "players" after doing such a fine job on this film. His portrayal of Detective Tom Polhaus was also spot on to what I pictured in the book.
Bond, Ward Bond.