Six Creepy Sheep

``Six creepy sheep said, `Let's trick or treat,' / one spooky Halloween night.'' So begins this sweet and simple holiday counting book by the creators of Six Sleepy Sheep . Clad in sheets, the sheep bravely go a-haunting, but when they encounter a passel of pirates, ``one creepy sheep turned tail with a shriek,'' leaving five. Their numbers continue to dwindle as they run across a flock of fairies, a herd of hoboes sp ok and so on, until a lone sheep remains. But in the end, sheep, pirates, fairies and all are reunited for an antic Halloween party. The snappy text, with its pleasing rhymes and alliteration, will have readers counting down as sheep after sheep flees the fold. The whimsical, mock-scary watercolors by veteran illustrator O'Brien are a particular delight. With his distinctive palette of silvery blues and violets, he portrays the bespectacled, sheeted sheep as they tiptoe past swashbuckling porcine pirates, donkey hoboes clad in patched overcoats and a ``warren of witches'' that look suspiciously like floppy-eared bunnies. Ages 2-6. (Aug.)