Boyd has a tendency to bite off more than the reader can swallow. It all begins well enough with academic Alex Ward and his crony, Ruth Gordon (70) at work on a rejuvenation formula. But Ruth takes the cure, becomes Diana/Aphrodite, and leaves a trail to Sunset Strip where Ward appears in various guises and helps stage an orgy of youthful grandmothers. Sugary, sniggery. . . .