I realize I risk being modded down, but there were many things that were NOT thoroughly explained in the HP books that the author of the lexicon explained rather clearly which is original conent. Also, JK herself has admitted to frequently using the lexicon while writing her later books to make sure she stayed consistent, so obviously the lexicon has value. JK also did NOT say she was going to make her own encyclopedia until AFTER the lexicon was going to be published. I love the HP books, but from all the interviews I've read with JK regarding this, it seems like a clear case of "that's a good idea, I want it for myself". The biggest thing that makes me roll my eyes and shout "OH COME ON!" is when JK said that if the lexicon was published, she'd never be able to write another book again.
Regardless of how this case turned out, after I found out about it I decided to never buy any more books written by JK Rowling due to her obvious insincerity when discussing why the lexicon needed to be prevented from being published.