From Theroux's lighter side: an all-American magician-as-Messiah fable that owes less to Elmer Gantry than to Tono-Bungay. When Jilly Farina, a 14-year-old waif from Marstons Mills, first sees Millroy the magician performing at Foskett's Funfair, it's codependency at first sight: Millroy, sweeping the girl along on his travels, provides her with a stability her minimal family life has lacked, and she gives him a sense of vocation he's never had. Jilly realizes early on that Millroy, who dresses her up as his adopted son Alex, is the real thing: a magician who knows the difference between tricky illusions and genuine magic, and who's mastered them both. ``Magic isn't an accident...It's good health,'' he tells her, and soon he's preaching his gospel of ``laxatives, Scriptures, and weight control'' on a segment of a Boston children's TV show, Paradise Park, and leaving a mike open long enough for beloved Paradise Park host Mister Phyllis to reveal to his network audience just how much he really loves children. Installed as host of the series himself, Millroy turns control of the show over to a bunch of kids, who send the ratings soaring before their frank discussion of Christmas and digestion causes its cancellation. Nothing daunted, Millroy fights off sponsorship offers from all manner of sleazy food-industry agents long enough to launch a string of high-fiber vegetarian diners based on the proposition that ``the Book will make you regular and grant you longevity.'' But the shadows lengthen: legal challenges mount up; Jilly feels Millroy withdrawing from her; and when a longtime acquaintance fills her in on Millroy's past, she lights off on her own--but is reunited with him just in time for an ambiguous apotheosis. Theroux's satire--waggish, broad, ambitious, spotty--keeps all the characters but Millroy and Jilly at a cool distance, and the relationship between them isn't nearly as engaging as it's apparently meant to be. Even fans may find themselves glancing at their watches.