Neither nowt nor summat.
Basically, this book tries to do too much and fails as a result. It attempts to present an overview of each of the world's best rock acts. To do that it spreads its net wide to encompass: alternative, blues rock, classic rock, country rock, experimental, glam (glam is rock?), grunge, hard rock, metal, folk rock, new wave, pop rock, progressive, psychedia, punk, rocknroll, and soft rock. It also, worthily, includes a number of bands from non-English speaking countries many of which most readers will never have heard of. By trying to cover all the bases it never satisfactorily covers any and numerous worthy artistes are omitted. Two examples: Stephen Stills isn't in (but Neil Young's there as is Buffalo Springfield), Echo & the Bunnymen aren't but The Teardrop Explodes/Julian Cope is. I'm sure any reader will find their own examples.
The book also lists the years active which in some cases is highly misleading. Example: Buffalo Springfield is listed as active 1966-2011 which is just ludicrous. They were only active for a couple of years and were really a springboard for Stills and Young. A couple of late reunion gigs don't, or shouldn't, count. Also 'active' is not a synonym for 'creatively viable'. Many artists are still trundling on doing live gigs where they play their greatest hits from many years ago. Example: As a creative force Chuck Berry (a truly great artist)was played out by the end of the 60s.
The overviews themselves aren't bad but you can read better on the website All-Music Guide.
It's a book for people to borrow from libraries rather than buy for themselves because it just isn't worth the money.