My 5 would be (in order in which I think they should be read):

Getting Started in Hold'em
Internet Texas Hold'em
Small Stakes Hold'em
The Psychology of Poker
Hold'em Poker for Advanced Players

I'd also recommend anyone to also read Weighing the Odds in Hold'em (this could be switched for HEPFAP if you don't feel too advanced) and Theory of Poker (to help gel all the constituant parts together).