Well, for my two cents worth, nothing compares to Brynes instructional videos. IMO, anything second to these, runs a very far second.
As far as watching the pros play, Accu-stats.com has all you could ever want. I think they are a vital part of training.
I believe one of the reasons so few folks play the game well is that they have never been exposed to SEEING how its done. Unlike baseball, or tennis, or even bowling, pool was always in the smoky back room. These videos of matches break that false impression of the game and allow some great exposure to the game that will help your play.
A book or two next to the old thinking chair can't hurt, but back to Brynes videos. They are a class act and can show you what you need rather than leave it to your interpretation as books do.
Books are a great reinforcement to things we already know about the game. But to learn fresh from the gitgo, there's no better way than to see it.
Private instruction is good, in fact, may be a needed portion of training in so far as catching bad habits before they develop beyond repair. But once you leave the lesson the visualization leaves you also. The videos can be replayed over and over at no additional cost.