Notes on Cowardly Lion is a biography of Bert Lahr by his son John Lahr. Not a tell-all like Christina Crawford's book, but he does not pull any punches about his distant and brooding (how like a comedian) but loving father.
Hollywood columnist Joe Hyams' biography of Bogart Bogie is worth reading, since Hyams knew Bogie and Bacall personally.
Robert Lewis Taylor's bio W.C. Fields: His Follies and Fortunes is a old-timey bio: lots of funny stories, no dirt or scandal or judgments, alcoholism of subject handled as the ordeal that it was for Fields. But worth reading for the funny stories, anyway.
Probably the best bio of a star I've ever read is Patricia Bosworth's Montgomery Clift: A Biography. She writes very objectively. Clift's relationship with his mother was...well, really something. Her biography of Marlon Brando is very good too, though very short.
Cecil B. DeMille: A Life in Art by Simon Louvish is well worth reading. A review is here.
Mailer's biography of Marilyn Monroe is worth a look to get the take of a great writer on a great celebrity. A review is here.