Adapted from the memoirs of Lennon's half-sister Julia Baird by Matt Greenhalgh (who's got a knack for tragic musicians, having written Control about Joy Division's Ian Curtis), the film is directed by Sam Taylor-Wood, and to her credit she does a great job with the film. There are several interesting images, and she brings out some terrific performances from the ensemble, particularly the always-brilliant Thomas. But visually, the film doesn't really stand out, and the sped-up scenes could have been done without. But the story is compelling, and the third-act reveal feels justly earned rather than contrived; credit this to the actors as well as to Greenhalgh's well-paced script.
Thomas and Johnson
Perhaps Nowhere Boy's best feature is its subject matter. Not enough has been written about how Lennon grew up with his Aunt Mimi, and his short relationship with his mother. Both women were hugely influential in his life, yet neither one gets much credit when people talk about him. And the film wants us to understand that, placing the main plot on John and his "mothers" while relegating the Quarrymen to a subplot (though it should be noted that Thomas Brodie Sangster, aka the adorable Sam in Love Actually, is still adorable as 15-year-old Paul).
Johnson and Duff
Overall, I recommend this film particularly to people who are interested in Lennon or the Beatles, though take note that this isn't about the latter group (the only reference to them coming in the film's final scene, and its a very opaque one) or "Give Peace a Chance."