There really is a book about everything. Tony Perrottet's Napoleon's Privates: 2,500 Years of History Unzipped (HarperEntertainment) examines the never-ending trend of popes (or politicians, or businessmen, or kings and queens) behaving badly, offering a catalog of prurience coupled with puns (mostly fairly bad, but often amusing anyway). There is, at least, a bit of historical mythbusting, and each section does offer a decent list of sources for further reading, should you be so inclined.
The bookish angle, of course, is the old story that a certain bit of Napoleon, lopped off at autopsy, was once in the possession of the great Philadelphia bookman A. S. W. Rosenbach (and later in the collection of the insatiable collector of the macabre John Lattimer, to whom Perrottet dedicates his book).
Useful (aside from the obvious conversation-piece factor) for its examinations of grist from the historical rumor mill.
