Compare "Foundation" with "Foundation and Earth" or "Foundation's Edge". Or "The Philosopher's Stone" with "The Order of the Phoenix". The former were well-edited and succinct. The latter were overly long, in some cases sorely repetitive with large amounts of padding, and a good editor could have cut them down by at least half without losing much.
And let's not even get into Robert Jordan...
Even the best authors need an editor.
