Smile If You're Human

English illustrator Layton makes his U.S. debut with this altogether prepossessing tale of interplanetary tourism. As a spherical orange spaceship comes to rest on a pale-yellow Earth sidewalk, the young alien narrator announces, ""I've brought my camera and hope to take a picture of a most unusual creature known as a `human,' "" while pressing against the craft's window with evident delight. Like any curious family, the extraterrestrial child, mother and father disembark and begin to explore what turns out to be a walled zoo. Unaware that the humans have dispersed (one image shows two cars speeding away), the aliens proceed to the animals' cages, earnestly consulting the ""Aliens' Guide to Earth."" The child checks to see if humans tend to bounce (""Mom looked at her book. `This jumpy fellow is a kangaroo. Humans like to walk' ""), and inquires about a four-legged, striped thing that readers will know as a tiger. Layton's gestural artwork may at first appear unsophisticated, but his cursory outlines and roughed-in swatches of paint serve to animate the ebullient pictures. The aliens resemble colorful patchwork bugs, with cheerful smiles, skinny legs and two eyeballs that wave high on thin stalks; conventional hats (e.g., a fedora for Dad) levitate in the air above their eyes. Their na vet is charming, particularly when they arrive at a gorilla's cage and make a small error; at least Junior gets a snapshot of someone's smile. Young Earthlings will surely giggle at these peaceful, flash-happy tourists. Ages 3-7. (Mar.)