During Valentine's week, second-grader Mattie exchanges an amusing series of gifts with a ``secret friend''--dreaded class rowdy Jeb--who is also her secret admirer; during spring vacation, she peddles pesky little brother Emmett, finds a taker- -and promptly realizes that she misses him; and, in a summer episode that links the other two, she and Jeb build a treehouse and give Emmett a disastrous haircut. There's not much subtlety here, either in the events or in Lehman's bold, cartoony b&w art, but the narrative is brisk and appealing, the plotting reasonably deft, the feelings genuinely childlike. A satisfactory early chapter book for kids not quite ready for the Haywoods. (Fiction. 6-8)
