'Jersey Boys' is about 'The Four Seasons' a music group ('rock', apparently. I don't know these things) in the late 1950s and early 1960s. Even if you don't know who they are, chances are that you would have come across at least on of their songs (I base that assumption on the fact that I've heard a few of their songs but never knew who they were by). The film follows these guys from their early days in New Jersey, to the peak of their success, and then the inevitable falling out.
The film doesn't try anything unusual or different. As I mentioned, it is a fairly standard biopic, and one of the ones that chooses to cover a few years meaning details are skipped out or left in the background while some transitions/gaps may be a bit hard to follow/fill in if you, like me, don't know too much about the subject.
Yet I found the film to be an amiable, easy watch. A little long, perhaps (it's over 2 hours), and uneven in places (I was a little annoyed as, at one point, the film did seem to start finding its rhythm before it suddenly takes a step back) but there was enjoyment to be had while Clint Eastwood's handling gives it more of a sincere feeling, and not in the overly sentimental way he has been guilty of in a couple of his other recent films.