With all the fictional characters penning real books out there, it’s a wonder there’s any room in the publishing industry for actual authors. Compared to TV shows and films, books are relatively cheap to produce, making a book penned by a beloved character a great promotional item. Some recent examples: in Mad Men, Roger Sterling (John Slattery) dictates the memoir “Sterling’s Gold: Wit and Wisdom of an Ad Man,” available in the real world from publisher Grove Press. Leslie Knope, Amy Poehler’s indefatigable deputy Parks Department director at the heart of NBC’s Parks and Recreation, recently published “Pawnee: The Greatest Town in America” through Hyperion. And all of the books written by Richard Castle, the pulp novelist protagonist of ABC’s hit drama “Castle,” are available in mass market paperback.