Can't believe I've only just discovered Chris O'Leary's writing. His blog, 'Pushing Ahead Of The Dame' is a university level biopsy of every Bowie song. You could spend days browsing it.
In fact it's so good he's re-edited it and re-written into an amazing Bowie book, my new favourite Bowie book. Available from Amazon or other sellers as listed the authors site. If you're a Bowie fan you really should investigate. Don't just take my word for it, do it!