Past the cutesy title--a car-window comminiquâ€š to kids in another auto--and 13-year-old Boo Hedley's equally cutesy nattering about where to start the story (""especially when it's from real life and not just make-believe""), this artless book has its points. Boo, her illustrator-mother, and her science-whiz little brother Jonathan, always on the move (Mom's cure for depression), fetch up this time in Virginia horse country; and, to make friends, adaptable Boo falls in with ebullient neighbor Tamara's plans to turn her into a champion beginner-rider--Greenway Stables contender in the older beginners' class at the annual show with ""ritzy"" Shadow Hills Club. But that clichâ€š situation serves only as a backdrop for Boo's growing ease around horses (half of horsemanship, we're reminded salutarily) and her ongoing concern about her relationship with popular Tamara and the other stable regulars. Shall she warn Tamara that personable Troy doesn't think of her as a girlfriend? Shall she follow Tamara on a rash scouting expedition to Shadow Hills? And the outcome of the big show turns far less on Boo's performance (mounted on an unfamiliar horse, she's thrown in one class) than on the fright of two Shadow Hills starlets at brother Jonathan's pet snake. The plotting could be called amateurish or, more kindly, inconsequential; when the book isn't trying--when, say, Boo and her mother are pooling their worries over a Chinese dinner--it has a pants-seat integrity.