J.K. Rowling's voice comes out pretty distinctively in the Harry Potter novels – if you've ever read an interview with her, you can definitely hear hints of the narrator who guides us through the vivid world of Harry Potter.
Our third person narrator is funny, with a pretty dry sense of humor. He helpfully explains weird wizarding world things to us Muggles, carefully relates all the action to us, sits back to let the characters talk (sometimes for pages on end), and gives us clues to help us along with the book's various mysteries. This narrator isn't totally omniscient, though – the action is largely filtered through Harry's perspective. We see other characters as they come into contact with him, we hear what he hears, and we experience his thoughts and feelings. Which isn't surprising: these novels are called "Harry Potter and Whatever" for a reason.