This book is just a compilation of other sources such as the (not altogether reliable) Scott Walker: Deep Shade of Blue, as well as The Impossible Dream: The Story of Scott Walker and the Walker Brothers (the Anthony Reynolds book), plus interviews culled verbatim from the Stephen Kijak documentary 30th Century Man and other more recent interviews with Walker published when Bish Bosch came out.
I found this rather irritating because even though Stephen Kijak and the other sources are credited in the bibliography, when these interviews come in the book they are not followed by a footnote explaining where they come from, which I found disingenuous because it leaves the impression the author led them and it's not the case.
Also the author is clearly totally out of his depth when tackling the latter part of Walker's career, struggling to understand his current musical and extra-musical influences. It would have been nice to know more about the contemporary classical music Walker is interested in to give the reader more context, for example.
Also as a latter-day Walker admirer, I'm always surprised nobody goes into other kinds of non-conventional post-rock music (you know, everything from Throbbing Gristle to contemporary Death Metal) that uses non-conventional vocals to drown out all the complaints that "his current music is weird, man!"
Aside from this, if you're totally new to Scott Walker's music and want to go a bit deeper than his Wikipedia entry, the book can give you an overall introduction to his work.
But I think anybody who really likes Walker's music and especially his latter output since Climate of Hunter would be better off watching the Kijak's documentary, reading the interviews published recently (some of the radio interviews are available on YouTube) and more importantly listen to the Tilt/The Drift/Bish Bosch trilogy.