If I told you that “Adam” was about a man with Asperger syndrome, a form of high-functioning autism, you would instantly lose all interest in seeing it, right? Yeah, that’s what I thought. If Fox Searchlight’s marketers are smart, they’ll keep a lid on that aspect of the film, because it’s actually a humorously bittersweet story buoyed by likable performances, and not an oh-geez-here-comes-another-film-about-a-saintly-disabled-person movie.

The Adam in question, played by Hugh Dancy, is an electronic engineer whose current job has him working on a toy company’s new talking doll. Adam’s father has just died, leaving him alone in the spacious Manhattan apartment they once shared, with Harlan (Frankie Faison), a family friend, to keep an eye on him.

Adam can mostly take care of himself, though. People with Asperger — Aspies, as Adam calls them — take things literally and have trouble knowing what other people are thinking, and they tend to misread facial expressions. Aside from that, they do OK. Adam is happiest when following a routine, and he gets particularly excited by astronomy. He doesn’t seem much different from your average nerd.

The new tenant in his building is Beth (Rose Byrne), an elementary school teacher who is immediately fascinated by Adam’s quirky personality, not realizing it’s an actual mental disorder — and after all, where is the line between “interesting” and “diagnosable”? Adam and Beth begin a tentative friendship and eventually a romance, though both are aware that such an arrangement will be difficult at best. Beth’s father (Peter Gallagher), a corporate accountant who’s just been indicted for shady bookkeeping, is adamantly anti-Adam for that reason.

Beyond addressing the elements of Asperger that I’ve already mentioned, the film doesn’t dwell on the particulars. It’s a story about two people, one of whom happens to have the condition, and while Asperger plays a part in how they interact, it isn’t the focal point. This isn’t some cheesy TV movie about a wise “special needs” person who teaches life lessons to those around him. On the contrary, writer/director Max Mayer (whose only other film, “Better Living,” was a decade ago) is not afraid to show Adam in a negative light on occasion, or to have Beth lose her patience with him. I don’t know if “realistic” is the word I would use to describe the plot — it is at heart a romantic comedy about cute people behaving cutely — but it does break free from some of the stereotypes, and the characters are believable.

Central to the film’s success is Hugh Dancy’s smiling, earnest performance as Adam, a role that easily could have turned one-dimensional and sappy. There is much to admire in Rose Byrne, too, who has chemistry with Dancy and a girl-next-door sexiness of her own. As a pair, Dancy and Byrne are easy to like.

The subplot involving Beth’s father feels like a tangent, contributing little to the movie’s major themes (though it does give us a chance to enjoy Amy Irving as Beth’s mother). It isn’t a life-altering movie, nor an overwhelmingly powerful one — but neither is it trying to be. Rather, it’s a simple, light comedy with dramatic underpinnings, and a pleasant way to spend an evening.

B (1 hr., 35 min.; PG-13, moderate profanity.)