As in her previous holiday packages (simultaneous book publication and TV production), Gail Rock's Valentine story is commonplace--motherless Addie, now thirteen, develops a crush on her new male teacher but comes to appreciate the attention of a boy her age, at the same time having to accept that her father has a girl friend--and her effects are on the slick side. But she does have a disarmingly plain manner and a good memory of small town Nebraska in the late '40's. There's the familiar school gym serving awkwardly as a seventh grade dance hall, the after-school hangout where the day's important encounters occur, and, just as recognizable, the widowed hairdresser (Dad's friend), fun-loving and a bit too flashy for Clear River in her blond (bleached?) upsweep and her painted toes in their wedgies. And those to whom the TV tie-in is an inducement won't mind that Addie's experience is standardized for an impatient mass audience.