Neil Gaiman gives his opinion in regards to fair use and the J. K. Rowling copyright law suit. He indicates that he’s all in favour of fair use, with the lawsuit covering a very grey area of the law. He cannot imagine himself being involved in a similar situation.

Fair Use and other things – Neil Gaiman: Lots of emails from people asking me to comment on the JK Rowling/ Steve Vander Ark copyright case. My main reaction is, having read as much as I can about it, given the copyright grey zone it seems to exist in, is a “Well, if it was me, I’d probably be flattered”, but that obviously isn’t how J.K. Rowling feels. I can’t imagine myself trying to stop any of the unauthorised books that have come out about me or about things I’ve created over the years, and where possible I’ve tried to help, and even when I haven’t liked them I’ve shrugged and let it go
Given the messy area that “fair use” exists in in copyright law I can understand the judge not wanting to rule, and assume that whatever he says the case will head off to the court of appeal.
My heart is on the side of the people doing the unauthorised books, probably because the first two books I did were unauthorised, and one of them, Ghastly Beyond Belief, would have been incredibly vulnerable had anyone wanted to sue Kim Newman and me on the grounds that what we did, in a book of quotations that people might not have wanted to find themselves in, went beyond Fair Use. (Which, I was told by my UK publishers, has now, as a concept, vanished from UK copyright law, although a moment’s Google seemed to disprove this.)