Three weeks ago, a tiny little novel with a cute title The Guernsey Literary and Potato Peel Pie Society started storming best-seller lists, and, driven largely by word of mouth and a sweet backstory, it now has over 200,000 copies in print. (That's a lot.) The novel, which follows the WWII-era exploits of a Nazi-foiling book club, was begun by Mary Ann Shaffer but finished by her niece, Annie Barrows, after Shaffer got sick (she died in February). And now, EW has exclusively learned, movie rights have been snapped up by an unusual partnership: Hollywood producer Paula Mazur (Nim's Island) and Florida bookstore owner Mitchell Kaplan. ''The story is about [a book club], so it's nice to keep the movie within the family of book-sellers,'' Barrows says. ''I hope Mary Ann is up there watching all this, and taking pleasure in it.''