It reminded me a bit of Orson Scott Card's Alvin Maker books, which also feature a magical America from a few decades later in an alternate timeline. Finlay, however, is less mystical, less didactic and basically less annoying about it; where Card is retelling the biography of Joseph Smith, Finlay is using an intense knowledge of the setting to hang his plot on. There are also perhaps faint reflections of Buffy, with the young hero discovering mystical powers and dealing with family and love-life. (One thing Proctor Ward lacks, however, is a Giles-like mentor.)
Good marks for sense of place; slightly cheeky to have the hero not only fire the first shots at Lexington but also save the day at Bunker Hill; but in general the history doesn't get in the way of the story, making it an enjoyable read.