Sourdough is bolstered with the prequel novella The Suitcase Clone, never before available in print. The new edition of Mr. Penumbra’s 24-Hour Bookstore likewise has the prequel Ajax Penumbra 1969 bundled in, along with a new foreword from Paul Yamazaki, the legendary City Lights bookseller who could easily be a character from the novel. He might, in fact, out-Penumbra Mr. Penumbra.