The Summer Before the Dark by Doris Lessing

As the summer begins, Kate Brown — attractive, intelligent, forty five, happily enough married, with a house in the London suburbs and three grown children — has no reason to expect anything will change. But when the summer ends, the woman she was — living behind a protective camouflage of feminine charm and caring — no longer exists. This novel. Doris Lessing’s brilliant excursion into the terrifying stretch of time between youth and old age, is her journey: from London to Turkey to Spain, from husband to lover to madness: on the road to a frightening new independence and a confrontation with self that lets her, finally, come truly of age.