Magriel's book is excellent, and it's not too dense for an absolute beginner. It's hard to find a book like that—one that's suitable for someone that's never played before in their life, and that's suitable for a professional trying to improve their game. I've only briefly skimmed one of them, but I understand Bill Robertie's books are quality, and his sub-forum on 2+2 is a good read, as well.
But definitely start with learning the opening moves. A lot of expert-level books in the past have disagreed on which opening moves are best, but BG sims have come so far in the last two decades or so that there can be no more dispute, at least from a pure EV standpoint (obviously, situations where you're playing with an overly aggressive or passive opponent will warrant different opening moves, such my favorite: the 5-1 roll to move 13/8, 6/5).
Edit: here is a good link explaining the problem of opening rolls, and it gives equity calculations, as well:
http://www.bkgm.com/openings.html
Then it would be helpful to learn about "counting" in BG, meaning the counting of pips and outs. You won't always need to use this, but it's useful when you don't know the correct move.
Finally, spend a lot of time practicing your cube strategy, which is one of the most crucial aspects of winning BG play. An average player with good cube play will beat an otherwise very good player with poor cube strategy in the long run. It's very similar to the concept of bet spreads in card counting.