Tangled Webb

``Don't try to pull the wool over the eyes of astute middle-graders'' might well be the moral of this engaging tale. Almost 13-year-old Juniper Webb is surprised when her widowed father suddenly marries Kelsey, who looks even younger than her claimed 25 years. Juniper does her best to get to know her new stepmother but, as she confides in the diary that forms her narrative, ``I don't think she wants me to know her .'' Disturbed by Kelsey's strange behavior and obviously invented stories about her past, Juniper delves into ``The Kelsey Mystery,'' aided first by her best friend Alison and then by Pete, a newly returned childhood buddy. Juniper and company unsnarl quite a tangle, but all is happily resolved, with the adults taking over when the kids get in over their heads. With McGraw's ( The Seventeenth Swap ) sure artistry it is easy to believe that Juniper's lively and unaffected diary is that of a real preteenager. Just as endearingly believable is the special relationship she has with Alison, whose African American heritage is less of an issue than the Oregon weather that forms a backdrop to their activities. Ages 10-up. (Apr.)