Twenty years after the release of the New York Times Bestseller “The Perks of Being a Wallflower,” author Stephen Chbosky is back with his second novel, “Imaginary Friend.” The novel is a stark contrast to Chbosky’s previous work, as he delves into the horror genre. In promotion of the new book, Chbosky stopped by the Carnegie Lecture Hall in Oakland on Monday evening to read an excerpt from “Imaginary Friend” and answer questions from fans.