THE MAGIC DAUGHTER: A Memoir of Living With Multiple Personality Disorder by Jane Phillips (Viking: $22.95; 238 pp.). Thank God there is some humor in this testimony to life inside a single body with several personalities, a crew that Jane Phillips and her therapist refer to as "the Kids." "Sometimes," she writes of the book's creation, "I felt like a journalist who, by sheer dumb luck, had found herself smack in the middle of an important story." Unfortunately, this is the kind of disassociation that Phillips has felt throughout her childhood and through her mid-30s, when she begins the therapeutic process that will allow the children inside her to grow up feeling secure and protected, a luxury that Phillips, whose list of childhood abuses ranges from subtle to terrifying, never had. In real life, she is an associate professor of French, in real real life she is a woman so beset by terrors, in such bitter control of her buried memories, that you cannot imagine she makes it through a meeting. "A child creates multiple selves," she writes, "to keep her deadly secrets out of the way of her conscious mind so that she can continue to function and survive." Through therapy, she comes to realize that "multiplicity is the problem" in her adult life, "no longer a solution" created by an unprotected child.