Is this a good idea for a book?

A girl moves from LA to NYC. She goes to a magic show, where the magician chooses her as a volunteer. The trick involves a bracelet, which has a magic charm on it; he lets her keep it. It brings her to a magical world filled with pixies, magicians, faeries, leprechauns, etc. It turns out that she is a magician, and the guy from the show is her mentor. There is a bad guy who wants to take over NYC, kill off all humans, and turn the entire world magical. not sure about the last part. any good?