One critic by the name A.S. Byatt refers to the novels as "derivative manipulation of past motifs." She believes the novels are only worth acclaim because they are based on a framework serup by authors like T.R.R. Tolkien, C.S. Lewis, and Roald Dahl. She had given an interview showing her virews on the popular series, it can be found here.
Other critics believe that Rowling create a completely new, imaginative world.