The point at which paper will spontaneously ignite without exposure to a flame is about 480 degrees, but this varies with the type of paper used and its physical properties. Once lit, paper burns much hotter. The center of a paper fire may reach 1,500 degrees or more.
While Ray Bradbury's science fiction classic "Fahrenheit 451" got its title from what Bradbury believed to be the auto-ignition point of book paper, modern experiments indicate that the true combustion point is higher. The actual temperature at which paper burns depends on its volume, composition, density and shape and on the length of exposure to high temperature. In an oven set to 480 degrees, a sheet of paper would catch fire and burn much faster than a thick book.