When a health scare puts him in the hospital, Eric Weiner-an agnostic by default-finds himself tangling with an unexpected question, posed to him by a well-meaning nurse. "Have you found your God yet?" The thought of it nags him, and prods him-and ultimately launches him on a far-flung journey to do just that. Weiner, a longtime "spiritual voyeur" and inveterate traveler, realizes that while he has been privy to a wide range of religious...