Talk about science fiction: Stephen Hawking, author of the million-selling "A Brief History of Time," is writing a "middle-grade" novel. "George's Secret Key to the Universe," the story of a young man's computer-driven adventures, will be published this fall by Simon & Schuster. "We are thrilled that Professor Stephen Hawking has written this one-of-a-kind book for children," Rubin Pfeffer, senior vice president and publisher of Simon & Schuster Children's Trade Publishing, said Thursday in a statement. "Just like 'A Brief History of Time' inspired millions of adult minds around the globe, 'George's Secret Key to the Universe' will make this complex material readily accessible to a younger audience." The book, co-written with Hawking's daughter, author Lucy Hawking, is the story of a boy named George who befriends a scientist and the scientist's daughter. George soon "finds himself on a wildly fun adventure, while learning about physics, time and the universe."