Its portrait of an easy-target industry goes soft just when it needs a little added spine, while the film’s abrupt tonal transitions from jaunty comedy to cross-generational weepie occasionally come at the expense of the characters’ own credibility. But it’s the overarching niceness of “Best Sellers” that sees it through.

Its script is undercooked and veers in random directions from its simple premise. But it has a heart, and two likeable leads who work well together.

Most of Best Sellers’ problems have to do with structure instead of performance, so there’s not much that Plaza and Caine can do. They’re stymied by the writing and constricted by the direction.

Clichés abound and you think you know where this is going. But in her feature debut, Canadian director Lina Roessler manages some genuine surprises. Caine is wonderful, Plaza is charming. The film has its moments, but one for the books this ain’t.

You’d have to go pretty far wrong to get me to pan anything pairing up Plaza with Caine, and Best Sellers tries its best, at times. But Caine does a grand grump, and Plaza reaches beyond her repertoire of eviscerating, man-eating side-eyes. They make this page-turner worth sticking with until the bittersweet end, and that’s enough.