The Black Libram of Nartarus is a DM's supplement for Castles and Crusades focusing on the dark art of necromancy.
Structurally this 35 page softcover is divided into 5 sections. The first is 2 pages long, and discusses the necromancer as a quasi-class. It's an interesting mechanical feature where to gain necromatic powers on top of whatever spell casting class powers you'd normally get, you spent XP. Why it isn't an additional XP cost to each level? Maybe so you aren't locked into it at every level? It's as clear as mud, which they literally point out...
There are also 3 additional powers that aren't locked by level to gain a bonus on saves vs undead, the ability to control undead (clerics only), and the chance to necrotize their flesh for an AC boost. All 3 powers, and upper level spell casting levels, come with charisma/reaction penalties.
The second chapter is spells. These spells are alphabetical, ranging in levels from 1 to 9. And then there are 2 more selections of spells from 2 specific spell books. Each of these are also listed alphabetically, but separate from the others. I really don't know why all the spells weren't put into one big list, and then the specific spell books listing out the spells they contain. Or even having the spells marked to show which books they're included in.
There's no index of spells by level. Also the 4th spell is missing it's name and level.
Sacrificial magics are covered in the third chapter, which takes up all of a single page. Nifty way to boost a spell caster's power by killing people or animals. There's also a bit about willing sacrifices, and a mention of innocent sacrifices, but those aren't covered. A reprint of the cover image takes up about a third of the page, and examples another third, so this is a pretty thin chapter.
New magic items are detailed in the fourth chapter, which is slightly longer than the third, and contains 9 new magic items. Nothing particularly noteworthy here.
The final chapter covers artifacts and relics. Actually, it only covers one, the titular Black Libram of Nartarus. As an example of a powerful book of necromancy, it works, and probably deserves the page it gets. As to whether it deserves it's own "chapter" is another question entirely.
Chapter 6 is monsters, and aside from the spells, this is the longest chapter in the book. Not hard to do, since the previous 3 chapters were about a page each.
Wait... weren't there only 5 chapters? Well, that's what we were told in the introduction... yet, here were are at 6. This chapter proves some aquatic versions of some standard undead, shadow animals, and a few old standbys like barrow wights, crypt things, and demilich. I do rather like the goat and the red jester though. Bright spots in an otherwise uninspiring and amateurish book.
As for the art... The poor cover image is repeated inside as I said before. What I didn't mention, is that it's used TWICE inside the book. The image on the back cover is also repeated in the book. There are 21 other images, mostly monsters. None of them are particularly noteworthy, and give the impression of having been chosen from either prior works or from a collection of fantasy art off of RPG Now. Of the 6 women depicted, all are in some sort of bra/halter top, and 3 are victims, 2 are monster (including a floating vampire thing biting into some adventurer's belly armor?) and one is some sort of spell caster.
This book has issues. Beyond the incredibly poor editing, bland at best artwork choices it's also a specifically NPC-centric class book. It doesn't outright proscribe their use by PCs, but...but I really don't get the point. And if you're going to do it anyway, at least do it well, and The Black Libram of Nartarus just fails all around.