I have bought probably over 100 chess books, but I recommend these three chess opening books (Amazon has them):

Chess Openings for the Average Player (Tim Harding and Leonard Barden) Amazon.com: Chess Openings: Books: Tim Harding,Leonard Barden

Concise Chess Openings (Neil McDonald)

The Chess Advantage in Black and White (Larry Kaufman)

Why these three? Because they have a simplified plan on how to win, that you can remember.

Of course, you can always buy specialized books on particular openings, and of course you should upgrade to ChessBase 9 at some point, but for beginners any of these three books are great.

If I had to pick them in order, it would be Barden's book, followed by the quirky but fun McDonald book (that almost fits in your pocket, it's that small) and then the more scholarly Kaufman book. Some older books by Fred Reinfeld and Reuben Fine are also good for openings.

If you can get the program Bookup that also helps memorize the openings.

Note I don't include the books NCO, ECO or the Informants since these are not really books to 'teach' you openings, but more like references so that once you start playing, you can see what others have done (likewise for ChessBase 9).

RL