Free Press 304 pp., $29.99 Simon & Schuster 464 pp., $20.99 Memoir is risky business. Its reputation? Slightly dubious. Its vices? Vanity, indiscretion, omission. Don’t trust it, said Orwell, unless it reveals something shameful. Even then, you might wonder why someone probes their past, poking around in the attic of their psyche. Why not let demons rest? If anyone understands these hazards, it’s Joseph Epstein, a great practitioner and skeptic of personal writing.