The Odd Woman by Gail Godwin
Jane Clifford is in her early thirties, smart, attractive, and seemingly kitted out for life with a Ph.D., a job as a popular teacher at a midwestern college, and an affair with a married man. But Jane knows better. And she wants more. She knows what she wants -- passion, romance, 'an age of bustles and rustling silk, fine manners and literary soirees' -- AND what she doesn't want -- to hand her life over to a man. And after a lifetime of looking to books for the answers to life's conundrums, she seems to be finding only more questions . . .