TAOCP is a very thorough "text book" for people who really are interested in the subject matter. It's not really Knuth's goal to break new ground with it, but to compile the most interesting things he's found into a single work.

It's hardly the only thing he's done though. Even without TAOCP, he's one of the more prolific and accomplished computer scientists in history: http://www-cs-faculty.stanford.edu/~knuth/vita.html