'Elf on the Shelf' Author Sues Over Knockoff Dolls

The makers of some 'Elf on the Shelf' merch awoke to find a lawsuit ... courtesy of the woman who literally wrote the book on the holiday craze.

Carol Aebersold, co-author of "The Elf on the Shelf: A Christmas Tradition" ... made a fortune selling gear based on the book. But in a lawsuit she says Maureen and Manus McGee have been hawking knockoffs, and even participated in the illegal download of 'Elf' movies.

In the docs, Carol says the McGees even bitch about eBay yanking their listings -- because they're unauthorized -- insisting they have a right to sell their version.

Carol's elf co. is suing for every dime the couple's made in the elf game -- and yes, they want all the "counterfeit" dolls hauled off shelves.