Ask Walter Mosley what he does, and he'll say, simply, "I'm a writer." And he's written a lot: 52 books, about 30 short stories and another 30 or 40 articles, he says. While most writers specialize in one or two types of books, Mosley refuses to be constrained. He has written mysteries, science fiction, erotica, young adult fiction, plays, opinion pieces and essays. He has even penned a slim book that instructs would-be fiction writers on how to get started.