Look, the novel “About a Boy” is so satisfying, you should read it now. Afterward, you’ll have a really good movie waiting for you.

The bittersweet film captures the tricky tone of Nick Hornby’s book. Hornby, who also wrote “High Fidelity,” has a specific viewpoint that could be described as sentimental cynicism. Often funny and sad at the same time, his work depicts characters that achieve what they hope for, only to realize it’s not what they wanted after all.

Will (Hugh Grant) has engineered his life to perfection he has no attachments, doesn’t have to work, has an huge supply of snug-fitting sweaters that look great on him but it doesn’t feel perfect. Will begins to realize this when he lies his way into a single parents’ club, hoping to meet women and instead meets a kid named Marcus (Nicholas Hoult) who shows him that his life lacks purpose.

Directed by Paul and Chris Weitz, working in a drastically different vein from their “American Pie,” “About a Boy” makes emotional and visual parallels that help us understand the connection between Marcus, who knows he needs someone in his life, and Will, who pretends he doesn’t. The idea of a kid with important lessons to teach an adult sounds smug and corny, but it isn’t because the characters are so well-conceived and because Hoult is such a wise-and-adorable-but-doesn’t-know-it marvel.

The Weitzes are so assured that they’ve dramatically altered Hornby’s novel and still managed to capture its essence, with invaluable help from Badly Drawn Boy, whose sad/sweet songs explore the moods of the characters.

“About a Boy” occasionally feels contrived (the clipped Grant and the mussed Toni Collette are too clearly meant to be opposites, for instance), but even that works in its favor, since this is a movie that says the best lives aren’t perfectly neat or perpetually messy; the best lives are the ones that are always racing between the two extremes.