The Brandeis Hoot has a review of sorts. "Huge impact on the world of classical music" is debatable. He wrote a smallish number of very good pieces but had a 40-year composer's block; he taught many students, some of whom became terrific composers, many of whom loved and learned a lot from him. But "huge impact"? I reserve that kind of hyperbole for people on the Bernstein or Copland level.
Updated October 5 and moved to top of queue.