Peter Matthiessen’s final novel comes out today, three days after the celebrated author and naturalist died of leukemia at the age of 86. In his twenties, Matthiessen helped found The Paris Review, which he later admitted using as a cover for spying on Americans in France as a CIA agent. He wrote more than 30 books, including “In the Spirit of Crazy Horse,” about imprisoned Native American leader Leonard Peltier. The book prompted lawsuits from an FBI agent and a former governor of South Dakota, both of which were later dismissed. He is the only writer to win the National Book Award for both fiction and nonfiction. His last novel, out today, is called “In Paradise.”