Birre, unbelievable, and quite a change for de Polnay whose two earlier books ran to caustic comedy. The magnificent idiot is a congenital mental deficient, known as Boo, whose primitive simplicity and inarticulateness held strong attraction to certain women, one of whom left him a fortune, the other of whom married him. His father, butler to the woman who made Boo her heir, guarded him through the years, furthered the marriage, and protected him even when he murdered a writer, whose malevolence he sensed. Perhaps this is a brief for a return to nature, without fears, complexes, and with instinctive responses that were right. Perverse, provocative, no more. Not for libraries.