I have read Stephen Davis' Hammer of the Gods, Richard Cole's Stairway to Heaven, plus biographies on Jimmy Page, Peter Grant, and Pamela DesBarres' I'm With the Band.
This is easily the best book on Zeppelin I've ever read.
Where most books on Zep fail is that they are usually chronologies written after the fact, by people who weren't there. Cole's book is the exception in that regard, but Wall's book goes much further than Cole's. Wall may not have been with Zeppelin every step of the way like Cole, but he did have access. He draws on many first-hand interviews he himself conducted with the band over the years to paint what is the clearest picture Led Zeppelin I've read yet. To Wall's own interviews, he also draws expertly from the other books I mentioned and countless other sources to tell the story. He does so in an extremely organized and effective way, by pulling the right quote from the right source at precisely the right time to make the point and move the story along.
What is even more effective, however, are the areas where Wall takes some artistic license and writes sequences using 2nd-person voice that attempt to capture what was going on in each member's head at different stages of their careers:
You are Jimmy Page. It is 1968 and you are one of the best-known guitarists in London -- and one of its least famous. Even the past two years in the Yardbirds haven't brought you the recognition you know you deserve. People talk about the Yardbirds as if Jeff Beck was still the guitarist, not you; despite everything you've done for them; giving up the easy-money session gigs that bought you your house by the river; gifting them one last ride on the merry-go-round with ahead-of-the game hits like Happenings Ten Years Times Ago.
While these sections may seem like a risky journalistic leap into guesswork, Wall pulls off them off with such remarkable plausibility that they actually add a lot to the read. With these sections, Wall has provided a key element missing from every previous biography of Zeppelin including Cole's: The motivation behind the men and their actions. The human factor.
When Giants Walked the Earth chronicles the lives of Jimmy Page, Robert Plant, John Bonham, John Paul Jones, and Peter Grant from pre-Zeppelin though 2009, including the various reunions, Page at the Olympics, and Plant's success with Allison Krauss. Well-written, very well-organized, supremely fair in the presentation of all that was both good and bad about Led Zeppelin. No topic was taboo, from the legendary road stories to the countless charges of musical and lyrical plagiarism, to Page's never-before-so-well-documented fascination with Crowley and the occult. Wall shines the light on all of it and largely lets the reader draw their own conclusions.
The most accurate and complete story of Zeppelin likely to be told, and a great read.