THE SUMMER BEFORE THE DARK by DORIS LESSING 273 pages. Knopf. $6.95.
This is a book about what Doris Lessing, as always with a straight face, describes as "a pretty, healthy, serviceable woman." Her name is Kate Brown. She is upper-middle-class English. Unlike most Lessing women, who are versions of Lessing herself, she is no intellectual. She is bright, though, and at 45 has long since acquired at some pain those caring virtues necessary to bring up a family: "Patience, self-control, self-abnegation, selfdiscipline, chastity, adaptability to others."
This is also a book...