Speaking as someone with a huge and ever-expanding music collection (and a particular interest in reggae), I've always found books of this nature to be of little value. This is especially the case now that we have access to an almost infinite source of reference material on this and pretty much every other subject under the sun, ie the internet.
The Virgin encyclopaedia is basically an A-Z of reggae and certainly contains a great deal of information. As such, it's an easy to use reference tool for looking up the biographical details or discographies of individual artists, groups and producers, as well as overviews of reggae's many different styles.
The biographical information is generally good, but unfortunately, the discographies are of very variable quality and ratings for individual albums can be somewhat dubious. There is a five-star rating system, and the vast majority of albums listed have been given either three or four stars. In fact I was surprised to see some major reggae artists without a single album with a five-star rating. In addition, each album is rated only in comparison to other albums by the same artist. Thus a three-star album by Artist A could easily be better than a five-star album by Artist B.
Another failing is the complete lack of photos, but the principal one is the lack of context. This is not a book which will really help you to learn about or understand reggae. For that you need an account of the subject which contains all the above information, but also chronicles the development of modern Jamaican music and of Jamaica itself, as well as the evolution of reggae abroad and it's influence on other musics....
So I'd strongly advise you to acquire the excellent "ROUGH GUIDE TO REGGAE" (by Steve Barrow et al) or the authoritative "BASS CULTURE: WHEN REGGAE WAS KING" (by Lloyd Bradley) in addition to or instead of this book. Or better still, forget about books entirely and buy the superbly documented 4 CD set "TOUGHER THAN TOUGH: THE STORY OF JAMAICAN MUSIC"; from which you'll learn more about reggae than from all the books in the world combined, while getting to hear some of the greatest music ever made....
The Rough Guide to Reggae 2 (Rough Guide Music Guides)
Bass Culture: When Reggae Was King
Tougher Than Tough: The Story Of Jamaican Music