With her swinging prose style and acerbic opinions, Pauline Kael was the most influential critic of the late 20th century. And as Brian Kellow calmly demonstrates in his rich, thorough, and ­admirably fair biography, she was a tough dame—she'd like that term—who worked out personal issues in her criticism. The author has assembled a trove of ­illuminating details, from Kael's young years in ­California to her oil-and-­water clashes with The New Yorker's painfully genteel ­editor William Shawn. —Lisa Schwarzbaum