Poker can be very lucrative but it is a tough game mentally. I played full time for a year and packed it up. Too much stress, as crazy as that sounds coming from a software programmer. I tracked it all and my database proves I'm a winner but at that time the game was dwindling and it just seemed like a tough future. Online in the US now is pretty brutal. Live is still a cake walk if you know your game.
My picks in this realm were Hold'Em Poker for Advanced Players by David Sklansky and Mason Malmuth (which seems to be out of fashion now as it dictates a pretty tight game) and also Mike Caro's Poker Tells book is quite good about the most common types of tell behavior you will see at tables and tourneys. It's up to you to determine if they're real or if someone is putting on a show.
I wish I could learn all over again :)