although Harrington on Hold 'em is for tournaments, it has some great poker concepts and I would suggest reading it just for ring games as well. Obviously you can ignore the sections about tournament structure such as the part on M's and such, but there was a lot of good poker theory I learned from that book and I primarily do cash games. Sklansky's NLHE book is also really good. Both assume you have a basic idea as to how to play the game and very basic strategy.
In terms of playing, I can't tell you much about casino play as I'm not yet old enough, but in terms of live games just know that first off announce your action, don't just throw chips in the pot, so if you want to raise first announce "raise", figure out how much you want to raise, verbally say how much, and then throw the chips in the pot. If you want to call, say call, then put the chips in the pot. That way you avoid string betting, accidentally calling by putting an oversize chip in, and miscounting and being bound to the action.
Also make sure you're patient. It's easy to be patient when you're online and can multitable, listen to music, and distract yourself a multitude of ways. When you're playing live it can be tough folding 80%+ of your hands. But if the players at casinos
are anywhere close to as bad as I've heard they are, to win you're going to have to play basic solid tight poker. Play good hands and bet them hard and they get paid off. And have fun, it's more fun when you win, but poker in general should be fun, and if you lose money during the session in Vegas it's not the end of the world.
So good luck in preparing and playing in Vegas, and have some fun and definitely let us all know how it goes