[Baulucky]

I recommend in this order:

1-Backgammon by Paul Magriel (There's a new edition). Expensive. The "old bible".
2-501 Essential Backgammon problems. Robertie. Cheap, good.
3-Advanced Backgammon Volume 1. Robertie. "New Bible part 1"
4-Advanced Backgammon Volume 2. Robertie. "New Bible part 2".

After you digest that, then some computer program like Snowie (Best, expensive) or Gnu or Jellyfish to really learn that computers are, for all practical purposes, the best at backgammon.(i.e.: Computers dominate all but the very best of opponents).