WORSE THAN THE WORST

Could anyone be worse than ``the worst person in the world,'' now so familiar a curmudgeon that's he's called simply ``the worst''? Indeed: small great-nephew Warren, whose parents (having, evidently, taken the measure of both miscreants) drop him off, without permission, for the weekend. The little hellion is as indomitable as he is rude; finding the larder bare, he sends out for pizza; he fills the worst's comfortably dusty old house with neighborhood kids and later commandeers the old man's own bed. Still, after a small foray into blackmail, Warren homes in on the worst's soft spot, and the two actually part as friends. A reliable premise, developed with Stevenson's usual wit and skill as a cartoonist and raconteur. (Picture book. 5-10)