Link (Thanks, Rick!)
In a statement, Rowling added: "It is not reasonable, or legal, for anybody, fan or otherwise, to take an author's hard work, re-organize their characters and plots, and sell them for their own commercial gain. However much an individual claims to love somebody else's work, it does not become theirs to sell."
Has J.K. Rowling ever been to a library? Seriously, I truly wonder. Because if she had, she might have seen many examples of exactly the sort of books she describes as "not reasonable." For instance, a list of the allusions in "Ulysses"; or a complete guide to all of the characters in William Faulkner's fiction; or a compilation and detailed analysis of Bob Dylan's lyrics; or a book containing the complete chronology of the events in David Foster Wallace's "Infinite Jest."
Hey, J.K. -- can I call you J.K.? -- these are known as "reference books," and, like the HPL, they are not mere "reorganizations" of characters and plots.
They are works of scholarship -- works derived from detailed study of an artist's creations, and intended to aid in research and appreciation of those creations. You might take a look at the fair use provisions of U.S. copyright law, which allow people to copy work for "purposes such as criticism, comment, news reporting, teaching ... scholarship, or research."