That a book which is always quoted in other books on Bowie bibliographies does not have any rating yet is rather curious.
This is a biography, a well, very well researched, one. If you were reading about Napoleon, or Elisabeth I, you will ask for facts. So should also readers of biographies of artists.
This book has not been endorsed by David Bowie, but it stands on its legs in an excellent way.
Writing style is spotless too.
I will say one of five books to own on DB, other than those devoted to pictures.
If you really wish to find a minor drawback in it, this is that it has never been updated, but then some may question if there is the need for such.