Nunn's Chess Openings (Everyman Chess Series)

In my opinion, Nunn's Chess Openings is every bit as good as Modern Chess Openings-14, which I also own. NCO is denser and has more lines, but MCO-14 is slightly easier to use. Both books compliment each other. It is very interesting to note how each book often differs in their evaluations of identical lines. If you're an intermediate player or stronger, I recommend getting BOTH!