Continuing her holiday series (A Valentine for You, 1991), Watson uses here the same appealing characters and New England setting, cozily set forth in an assortment of cartoon-style vignettes and more expansive illustrations; but this time she takes a somewhat different tack with a text that includes less traditional material: While the straightforward narrative describes preparations and kids making their trick-or-treat rounds, the characters (pets, too) in the pictures are asking riddle-jokes that bid fair to steal the show (``What...do ghosts wear?'' ``Boo jeans!''). A nicely understated change of pace from the more garish books for this holiday. (Picture book. 3-8)