"He says you'll never be hurt as much by being open as you have been by remaining closed."The messenger is a school janitor with a master's in art history who claims to be channeling "from both sides of the veil." "He" is Adam, a three-year-old who has never spoken an intelligible word. And the message is intended for Martha Beck, Adam's mother, who doesn't know whether to make a mad dash for the door to escape a raving lunatic (after all, how many conversations like this one can you have before you stop getting dinner party invitations and start pushing a mop yourself?) or accept another in a series of life lessons from an impeccable but mysterious source.From the moment Martha and her husband, John, accidentally conceived their second child, all hell broke loose. They were a couple obsessed with success. After years of matching IQs and test scores with less driven peers, they had two Harvard degrees apiece and were gunning for more. They'd plotted out a...