Printed in 2006, in time for the Robert E. Howard (REH) centennial, Conan: The Ultimate Guide to the World's Most Savage Barbarian, attempts to chronicle the Cimmerian's adventures throughout the Hyborian Age. This was a challenging endeavour since, Conan's fame exploded far beyond REH's original short stories. The book's chapters provide short synopses of the various stages of the Cimmerian's colorful life, from childhood and possible slavery, to an advanced age with a crown upon his head. The stories that fall outside the Nemedian Chronicles (REH's stories), are considered "legends."
Since I haven't read every Conan story written by REH and subsequent authors, I found this overview to be extremely helpful.
The book is also a sumptuous, visual feast of art, found in the plethora of books, comics and graphic novels. REH's Hyboria is much more sensual than other high fantasy realms, such as Tolkien's Middle Earth--which is why Conan appealed to me at a pre-adolescent age.
There are 23 reviews of this book on Amazon.com, but not everyone's happy with Roy Thomas's work. While the feelings are overwhelmingly positive, 20 x 3-star reviews, a few felt this book was more about the post-REH Conan, than the original works. While they have a point, I think they're missing the big Hyborian panorama: That Conan fans want to know more about "...the world's most savage barbarian" than it's creator could provide.