Nunns chess openings is impossible to understand, get Modern Chess Openings instead.
Nunns Chess openings

It works pretty much like this -
e.g
1 ... 2.
e4 e5 Nf3
Bc4
f4
c5 Nf3
d4
c3
d4
You read it by columns. At the top of the table, there is number indicating which move. So, the number on top of 'e4' of white's first move. Then it's black's choices, followed by more choices for white (the number 2 at the top indicates that it is the second move for white) and so on.

OK with the NCO here is what you do:
1. Pick the opening you are interested in studying and read the intro on it.
2. Each subsequent page is a variation(usually a named variation)
3. The chart indicating potential lines lists several opening lines with the best responses. It will list out the progression of moves in that line and indicate who is "better" by the last move, based on that progresion. All the other text is variants of these lines.
4. Promptly throw book in trash(or use as a doorstop) and get a copy of Modern Chess Openings as NCO is so hard to read! It is encyclopedic in nature, but not partiularly readable.

Dear friend,
Opening variations have a way of coming back.NCO is now 9 years old.But much of it can be useful. If you do not find it user-friendly, and space in the house a problem you may give it way.I have not see the latest edition of MCO.But I remember it was panned in chesscafe review.If you see checkpoint archives,July 2008, you may find the same.
The recent title FCO by the same publishing house, Gambit may be a reasonable alternative. There are two others: Mastering Chess Openings by Watson and Chess Opening Essentials set. It's your choice.All the three provide a wealth of explanation accompanied by current variations.
Well im new at reading Encyclopedia's, and basically weird opening books, such as this one..
i really dont get how to follow the openings, it has weird coloumns and rows of moves, can someone care to explain?