Against all odds, Portis sustains a single joke through an entire novel, piling outrage upon outrage in a wicked deadpan that is always on pitch. Although brevity is supposed to be the soul of wit. this novel only gets funnier as it careens crazily along. Best known for his True Grit (1968), Portis also has developed a cult following for his The Dog of the South (1979)--which may have givers him the idea of having a cult as the central joke of this tour de force. It is the sort of cult that attracts boobs, namely the Society of Gnomons, derived from the cabalistic lore of lost Atlantis and given to pointy hats, obfuscating utterances and loony rituals. The modern cycle of Gnomonism begins in WW I France, where a Yank doughboy--Lamar Jimmerson--is given the Codex Pappus and becomes an initiate and then a master. He in turn initiates the reprehensible Sydney Hen and marries his crippled sister Fanny. Lamar sets up the Gnomon temple in a suburb of Gary, Ind., but Sydney starts a schism that rends the society. In the 1930's a peppy go-getter, Austin Popper, gives Gnomonism a shot in the arm, and it is he who suggests to Washington that WW II can be won by compressed air. Washington turns a deaf ear, and it is more or less downhill for the society from then on. Popper is Portis' funniest character--worthy of Dickens--and his attempts at deriving gold from creeping bagwood with Cezar Golescu, Roumanian authority on the lost continent of Mu, provide some of the most hilarious pages. At a guess, the book will start a new cult--far larger than Gnomonism at its peak.