Gregory Maguire has built his own alternative universe with his series of Wicked novels. Premised on L. Frank Baum's Wizard of Oz tales, Maguire's tales give the stories of the Emerald City and Munchkinland a more contemporary, psychological spin, as well as regarding them from a decidedly cynical perspective.His latest title, Out of Oz, was a published early this month, and Maguire is in town for a 6 p.m. signing at Joseph-Beth Booksellers Wednesday evening. Since the tour of Broadway show based on his first novel is also in town, he'll be joined by Amanda Jane Cooper and Mamie Parris who play Glinda and Elphaba, as well as a few other cast members. They'll sing a song or two from the show. Of course, Parris won't be quite as green as she is onstage, but it's a chance to hear some of Stephen Schwartz's popular tunes from this blockbuster Broadway hit — just by showing up at the bookstore. If you want Maguire to sign a copy of the book, you need to buy it that evening to get a place in line.