I would say that for any experienced collector of classical CDs, or even a keen beginner who wants to seek out the best versions of a work, this book is next to useless. I can provide examples to support my case.
Take Shostakovich for instance. There are two sets of the complete symphonies listed, but only ONE version listed of the "Leningrad" symphony (No.7) that can be bought separately. This is the later LIVE Bernstein recording. Even this is part of a two disc set and the reviewer remarks on audience noise! At the time of writing, a look on Amazon reveals 178 entries for this symphony. I accept that quite a few of these will be duplicates or parts of boxed sets, but I think this makes my point. It's easy to find versions conducted by Kofman, Gergiev, Ashkenazy, Bychkov, Jansons, Masur and Barshai (the latter's whole set on Brilliant is outstanding) - not to mention the earlier Leonard Bernstein recording (sometimes hard to find, but well worth searching out). These are just a few examples.
Rimsky-Korsakov is granted a whole two pages in this book covering some of the better-known works. There's no mention of (say) Symphony No.2 (a lovely work) - and NO operas at all - staggering!
Bearing in mind that this book claims to review DVDs as well as CDs, Puccini's "La Rondine" does very badly. Although there's one CD listed (with Alagna), there are NO DVDs listed and I know of THREE - all good in their own ways. Giordano does no better: neither of the Domingo DVDs are mentioned and nor is the Cura version - and when it comes to the opera "Fedora" - well, it's not even mentioned! There is a beautiful Met. production with Freni which is well worth adding to your collection if you like the work.
If you want a book that does its best to cover everything and reveal the riches that ARE available, I would much rather recommend the Penguin Guide to Classical Music.