A good discussion here: http://www.slate.com/id/2181776/ 

A vast fan website tolerated by Harry Potter author J.K. Rowling has decided to publish a Guide to the Potter universe in book form. Rowling is now suing to block the publication on the basis of copyright infringement, claiming that only she should be able to publish a Guide. 

From what I know of copyright law, this case is going to fall flat on its face. Guidebooks have always been part of the literary landscape. From the Slate article: 

The closest relevant legal precedent is the 2002 Beanie Baby decision  by Judge Richard Posner (who has a taste for cases involving stuffed animals). Ty, the producer of Beanie Babies, doesn’t like unauthorized guides to the Beanie Baby universe and their unflattering tendency to criticize the company, so it sued. Ruling against the company, Judge Posner used the same analogy that I have, comparing the guides to book reviews: “Both,” he said, “are critical and evaluative as well as purely informational; and ownership of a copyright does not confer a legal right to control public evaluation of the copyrighted work.

It seems pretty clear, Rowling is not going to win this one.

B