Loses many of my favorite scenes from the book, but still pretty decent as adaptations go; writer-director Marielle Heller chooses to focus on the imbalanced sexual relationship at the story’s heart, making it clear she finds it emotionally exploitative (check out the repeated, clumsy references to the Patty Hearst kidnapping) while amply illustrating why a sexually active teenager would find it compelling and even romantic. Part of the reason is the presence of Alexander Skarsgård, so rakishly charming that you can understand why anyone would want to sleep with him, let alone a horny adolescent. For 80 minutes or so, this is an utterly credible depiction of a likable but awkward girl making some bad life decisions. But where the source material — a somewhat autobiographical novel with comic-strip passages by Phoebe Gloeckner — takes a sudden and harrowing descent into darkness, the film spends a few vacation days at the Sundance Institute before tying up its too-happy ending. If I hadn’t read the book, I’m not sure I’d notice that Heller botches the landing. Either way, Bel Powley is so good in the title role that it almost doesn’t matter.