The lot of families with sick kids is making normal out of the horrible. In My Sister’s Keeper, Anna (Abigail Breslin) nonchalantly saunters past a biohazard container sitting on the bathroom counter between girly accoutrements. Her sister Kate (Sofia Vassileva) has cancer, and Anna has been engineered by her parents — the desperate Sara (an appropriately beautiful-cum-ravaged Cameron Diaz) and Brian Fitzgerald (Jason Patric) — to be a designer bone-marrow source for Kate.

Although the premise here is that Anna will later sue her parents for medical emancipation (with the aid of lawyer Campbell Alexander, phoned in by Alec Baldwin), My Sister’s Keeper is no legal thriller. More than anything, it’s about the microcosms of a family under duress: the temperamental marriage; the sibling allegiances; the consuming, swooping ferocity of the “crazy-bitch fighter mom” (as the comic-relieving Aunt Kelly calls Sara). Based on a Jodi Picoult novel that the New York Times Magazine called “child-peril lit,” My Sister’s Keeper unfolds episodically, much of it in the blushed, gauzy tones that indicate perfect American happiness — the “before” era when Anna represented Kate’s only hope.

Typically, director/co-writer Nick Cassavetes chronicles the devastation of childhood illness — and the ways that it bends a family close to breaking — with an acute sense of emotional manipulation. There’s no real way around it, and no reason around it: movie audiences, as much as Picoult’s readers, want this catharsis, as artless as its telling might be.