So, today a book arrived for me- Lords of Madness. I got it for like $10 on Amazon, used (but pristine).
In terms of Books of Evil Shit that now puts us up to:
The Book of Vile Darkness
Fiendish Codex I: Hordes of the Abyss
Fiendish Codex II: Tyrants of the 9 Hells
Heroes of Horror
Lords of Madness
Of course, two more Evil-specific books are coming out this year (Exemplars of Evil, and Elder Evils) but, that's besides the point.
I think, aside from those yet unreleased, that just leaves Drow of the Underdark for Evil-Specific Sourcebooks. I'm excluding the numerous catalog of Dragons books (Draconomicon, Dragon Magic, Races of the Dragon)... well, because I don't give a shit about dragons. On the whole, I find 'em pretty stupid. Evil Outsiders= way cooler.
And yes, I understand that the game is Dungeons and Dragons. It (should) be Dungeons and Demons as Demons are the most prevalent of the foes, simply because there are waaaaay more things you can do with them then keep making colors of Dragons.
Ha, I just had to stop there so that I could update the Wikipedia article about D&D books (they were missing that last few Complete books, Heroes of Horror, and both Fiendish Codices.
Personally, as a Planar History n00b, I'm enjoying learning more and more about the Start of the Great Wheel (Aboleths= here before the gods) and its end, as well (Mindflayers= here after everyone else). And I admit, having taken both vertebrate and invertebrate zoology courses, seeing cross-sections and diagrams of abberation physiology is strangely amusing.