Adapted from Walter Kirn’s novel, Thumbsucker is graphic designer and TV-commercial director Mike Mills’ first feature, and it shows. Some of its filmic vocabulary, not to mention the narrative itself, seems right out of a Volkswagen spot, and the movie has a way of gloating over the subtlety of its humor that tends to undermine the subtlety of its humor. No, it’s not all bad, but it is, as indie fare goes, a little pat and generic. Mills does have the good sense to use an emphatically non-generic ensemble cast, including the increasingly ubiquitous Tilda Swinton and the not-ubiquitous-enough Vincent D’Onofrio as the parents of the eponymous protagonist, an abashed 17-year-old who still sucks his thumb and goes through some hell trying to knock it off. That would be Lou Pucci, whose disarming performance is what’s most alive in this film, and why it’s worth seeing.