The Affair by Lee Child Delacorte Press, $28.00, 405 pages, ISBN 978-0-385-34432-6      Unless you’ve been living under a rock next door to the guy in the insurance ads on TV, it seems as though everyone has heard of Child’s implausible hero Jack Reacher, “just about the best butt-kicker in thriller-lit” according to Kirkus Reviews.  Reacher’s almost Zen-like in that he owns nothing, wants nothing, and travels the USA