The trick here is to read the small print. The title boasts the qualifier of
"essential" reference guide and here that descriptive relates more to the bare minimum information than a must-have guide. As a basic compendium, this does the job - it covers all the great ones from Van Halen, Beck and Stevie Ray to David Gilmour, Robert Fripp and Steve Lukather. There just isn't a tremendous amount of insight, nor is there anything that we didn't already know about these luminaries.
In the chapter on Edward Van Halen, we're served up the usual born in Holland fare, Eddie licking his lips over Clapton's Cream, building his own guitars, et al. And? In one of the closing paragraphs, the authors write: ..."Few guitarists after Hendrix used the device (talking about the tremolo bar) so dramatically." What about Jeff Beck? Brad Gillis? David Gilmour (a gentle touch in comparison to these other bar benders but a master of subtlety nonetheless)?
In a section titled Landmark Rock Guitar Albums Through the Years, the authors have (and certainly personal opinion has its place) chosen a variety of discs including Zeppelin's Presence, John Mayall's Hard Road, and Cream's Disraeli Gears as touchstone recordings. How do you select these recordings in the place of Zeppelin's first, second or fourth albums, Mayall's Bluesbreakers, or Cream's Goodbye (or any of the subsequent live offerings)? As great as the author's selections are, they pale in comparison - and stature - to these other titles.
For an all-in-one reference, this is worth having. There are no quotes from the players themselves and that remains a tremendous hole in the presentation. But as a down-and-dirty modified encyclopedia, this works.