Someone in #chess was curious about MCO 15, since they just got their copy, so I went digging around and found this review on MCO 15, take it with a grain of salt.
Another review states: "Modern Chess Openings" is the best and most trusted tool for serious chess players on the market. First published over a half-century ago, this is a completely revised and updated edition of the book that has been the standard English language reference on chess openings. An invaluable resource for club and tournament players, it now includes information on recent matches and the most up-to-date theory on chess openings. "Modern Chess Openings "is ideal for intermediate players ready to elevate their game to the next level or International Grandmasters who want to stay on top of recent chess innovations.