Mostly everything Phil Gordon, David Sklansky and Ed Miller put out over the years. poker differs a lot in its variants, atleast to newcomers, so it's probably best to pick up one variant (no limit hold'em I'm looking at you) and start from there.
I like most of what he's written, so just to whet some appetites, I'll link to the FToP overview: https://en.wikipedia.org/wiki/Fundamental_theorem_of_poker