The biggest surprise of Sikov s perceptive and superbly written new Bette Davis biography is that there are still fascinating details to be discovered after more than a dozen full-length biographies have been devoted to her since her 1989 death. Sikov (On Sunset Boulevard) follows the volatile actress s long career, specifying how her insecurities and craving for love propelled her into the dueling self-medications of liquor and acting. Even she didn t seem to understand the anger that drove her to battle everything she encountered, from Hollywood producers to the tarnished brass doorknobs in her many houses. Her personal life was littered with broken marriages, affairs, abortions, feuds and neglected family members, but professionally she created dozens of unforgettable performances. Both sides of her life make for compelling reading. Sikov spends two-thirds of the book documenting the grueling production of most of the 52 films Davis made under her 18-year contract at Warner Bros. These illuminating tales mix familiar lore with newly excavated material. Sikov loses some steam when Davis s film career sputtered in the late 1960s. The last 20 years (when she was too ornery to die, too driven to sit still, too proud to recede into muted seclusion) is dismissed too quickly in 60 pages. Photos not seen by PW. (Nov.)