Hi,

I have just started to study openings and I am looking at Nunn's Chess Openings and Modern Chess Openings (MCO 13 to be exact because I can get it used very inexpensively)

Have you used these?  Which do you prefer?

I know that MCO is widely used but I have also heard good things about NCO.

Just curious.  Thanks.

Laser

NCO is clearly better than MCO 13.  NCO vs. MCO 14 is a horse race.  Of course MCO 15 is the most up to date if you can afford.  As someone that is just starting to study openings, you don't want a book that looks like a telephone book.  I think there are better books than either MCO or NCO to start with.  Also a starter book wouldn't get out of date so early.

http://www.chess.co.uk/twic/john-watson-reviews/mco-14-in-part-vs.-nco

I looked into MCO 14 and 15 but I heard they were littered so many typos it made them difficult to use.

Chess Opening Essentials by New in Chess is a fantastic 4 volume set. These books explain the ideas behind all of the major openings. Much more useful to you then variations without explanation. 

This may be going around your point but I  like the live book in Fritz 13 as so many top players are putting moves in its a very interesting opening book.

the way to think about this is what works.

Ideas help you understand the "why" of moves which helps you remember the "what" move to play.

To this you should work on the chess opening essentials series. also starting out series is a good choice as well. Start with one. I also like the chess stars books on openings  look for the ones that offer a step by step and in detail  in the decriptions. They are very well organized and can you off on a good foot.

Fine's book is good too, its opinion on the Lasker sicilian (aka sveshnikov is dated though due) but its still very relevent for its dealing with structures. 

Another book is horowitz book chess opening theory (dated but still a nice intro)

On chesscafe.com s book of the week they have cb opening book 2012 just out and being reviewed.

Fundamental Chess Openings is relative inexpensive and has some good reviews:

http://www.chessvibes.com/reviews/review-fundamental-chess-openings/