I would go for anything written by David Buckley as what I've read of his on Bowie is well-written, well researched and generally very accurately and objectively put together. He has a biography on him,
Strange Fascination.
http://www.david-buckley.com/books.htmlI haven't read it, but the latest Bowie biography is
Starman: David Bowie by Paul Trynka.
As an alternative read, I would seriously suggest Nicholas Pegg's
Complete David Bowie, now in it's fourth version I think, but any version will pretty much do, given that no new Bowie material has surfaced since 2003. This goes into great detail into the making of each album as well as providing the most in-depth, detailed discography, filmography and livography on Bowie to date.
It's a massive book though, and there's a similar book by David Buckley on a much smaller scale, purely focussing on albums and the story behind every song (
The Complete Guide to his Music).
I would also recommend
Bowie In Berlin – A new career in A New Town by Thomas Jerome Seabrook. As the title suggests, it focuses purely on Bowie's time in Berlin with Iggy Pop. A great read, and makes you want to play the albums non-stop.
Hope this helps...!