The only good book about black metal is Jon Metalion' Slayer fanzine anthology as far as I'm concerned. You get all the facts and evolution of the scene at the time they happened by an insider who doesn't need to try to get more credit by making shit it up, blowing things out of proportion or anything. He was there, he was friends with everyone, he chronicled it on time, from before its beginning to after it shook the entire world. The parts between the fanzines in the anthology are as authentic as it can get. Of course, he doesn't review or mention EVERYTHING so don't expect to read about say, the Polish TOF for instance. But when it comes to facts (and that's what history is about, right?), this is it. Everything else I read is biased as far as I'm concerned, and I don't see the point in publishing books that read like messageboards with guys trying to one-up each other, which black metal has always been about (well 97% of the time that is.)
There's a very fine line between aesthetics and posturing and the balance used to be right up until 20 years ago, I think. I mean, posturing was very much present in fanzines and band's attitudes but the outreach was pretty tiny. I think the internet changed the BM scene entirely and that music isn't enough to make bands stand out anymore because it's so much easier to record and put out music, to spread it worldwide too, and the overwhelming amount of information available does that to be remembered, bands need to focus on the posturing. And the internet amplifies trends too. I remember the time when Osmose couldn't even sell Blasphemy CDs for 2€ (I sure never bought any) and nobody really cared about them. Same with NSBM or war metal. It takes one intense nerd with a genuine interest and smart marketing strategies (and a few other people with good intuition) to change the course of everything, as evidenced by the bands that always get mentioned again and again and again on the messageboards he's not responsible for, as if any other BM bands had never existed for the last 35 years.
All this rant to say that I would take every book on BM with a grain of salt because they're always written with some agenda behind them and that the evolution/explosion of the scene from the underground as well as the people dwelling in it make everything difficult to trust or accept as true when it comes to facts. But they're good fun when it comes to fan fiction of course.
And thanks, ConcreteMascara, my pleasure.