PETROPOLIS

When the owner's away, the pets will play—and take an excursion to Petropolis—according to this furry flight of fancy from a brother-sister team. Max the beagle faces a day like any other, until he steps through the brand-new dog door his humans have installed for him. The portal leads to Petropolis, a bustling city completely populated by snappily dressed pets, enjoying themselves to the hilt. No "keep off the grass" or "not on the furniture" rules exist; it's all rawhide-crust pizzas and kibble sundaes at the "Slurp n' Burp." But a trip to the museum, which features a portrait that reminds Max of his family, soon has the pooch heading for home. The rhymes frequently fall flat, but the general upbeat rhythm of Whayne's (Watch the House ) story and the parallel-world imagery will keep readers interested. Santoro (Open the Barn Door ) adds humor into every available inch of his merry watercolor scenes: an art piece by Salvador Dogi, a fish on a motor scooter, The Scratching Post Card Shop. All in all, a diversion for those humans who imagine what the animals do in their absence. Ages 4-8. (Oct.)