There's really not any good books or documentaries on BM because so much of it focuses on the sensationalism of church burnings etc. Rather than the development and styles of the genre.
I see you're unfamiliar with Dayal Patterson's 'Black Metal: Evolution of the Cult' which was published in 2013. It's far and away the best thing ever written on black metal and I strongly recommend you check it out. It's massive, brilliantly written and presented, and he spent years on it. Check it out here for details:
http://www.cultneverdies.com/p/blog-page.html
And testimonials from pretty much all the key names in black metal and who are all in it too:
http://www.cultneverdies.com/p/reviews-and-testimonials.html (scroll down a little to read the 'Evolution of the Cult' testimonials).
As for 'Lords of Chaos', in 1999 when I first read it, it was simply fascinating. It has since received a lot of flak due to its sensationalism, but it's pretty hard to write a book expressly on two murders and a suicide without it sounding pretty sensational. I found it very entertaining.
But 'Black Metal: Evolution of the Cult' just leaves it for dead. Patterson has since published more interviews that he's done over the years in a follow-up, slimmer volume called 'Prelude to the Cult' but it's more of an addendum rather than a comparable piece.
His true meisterwerk, however, is definitely 'Evolution of the Cult'.
