Books are a little bit outdated, because they are so static. The rage these days are courses, and with the disclaimer, that I have not followed any of these, some of the most well reputated for intermediate players are:
* Upswing lab (Doug Polk and Ryan Fee)
* Daniel Negreanu Master Class
* Phil Ivey Master Class
With any of these you know, you are learning from big proven winners in the game, and that has to be a pretty good starting point.