If he is writing his own copy about Rowlings's work, that's okay. If he quotes indirectly, that's okay, too. If he is quoting in a limited way from her works, that is also fine as long as he stays under the upper limit allowed.

Everyone knows that there's a limit for the maximum length of a single quote. There's also a top limit for the percentage of the work that is quotations from another copyrighted work, regardless of the lengths of the individual quotations. It sounds as though he's gone over the acceptable percentage of direct quotes.

Copyright is so very slippery.