I used to own every D&D book from 3rd Edition, up until several months after the announcement of 4th Edition. One of these books was Libris Mortis, which was a book that went into extensive detail about undead. Personalities, diets, physiology, etc. Like all 3E books, it had a lot of crunchy material, from feats to prestige classes to spells that were thematically died to undeath. It even had several iconic monsters as classes if you wanted to all out. Going back I have to say that I liked the book in theory, but only ended up using it for the Corpsecrafter feat tree to make completely overpowered undead servitors.
Open Grave is a successor to that in that it’s another book on undead, though it doesn’t follow the same format: this book-of-ze-dead is intended for DMs only. Its divided into four chapters (with four being almost half the damned book) organized into undead lore, DM information, premade lairs, and (of course) new monsters.
The first chapter is a fairly interesting read, going into the origins of undead as they function in 4th Edition. My favorite thing about 4th Edition undead is how the body, soul, and animus relate to each other. I remember reading up on this in the Wizards Presents preview books and really digging this concept, especially since 3rd Edition had a lot of arguments about undead, negative energy, and evil (despite negative energy being completely neutral). While I don’t think the arguments will stop, I think that this new take on undead helps a lot of things make more sense.
There's a brief overview of decomposition and the how it works with undead, as well as how some undead like vampires can suppress it (vampires by drinking blood, ghouls by eating flesh). How their eyes work even if they don’t have physical eyes. Whether they can smell, why they eat, the morality of necromancy. I could go on, but Chapter 1 is a pretty big chapter.
Chapter 2 has a couple of new Skill Challenges that involve trying not to piss undead off, rules on hauntings, centering adventures or entire campaign arcs around undead, new artifacts and rituals, and undead grafts.
Hauntings are those parts in horror flicks where the ghost freaks out the main character for no real reason other than to be a jerk, or where they experience some kind of vision of a past event. You can use them purely for visual effect, but if you want to take it a step further the section provides rules on using them as reflavored-traps, hindering terrain, or even as part of a Skill Challenge (going so far as to add yet another Skill Challenge example for this purpose).
Artifacts has eight new artifacts, which include the sword of Kas, a murderous ioun stone, and an orb that really, really doesn’t like undead.
The new rituals include a method for creating an undead minion, which doesn’t do much except take up space and probably lift heavy things since it’s got a Strength of 16. Another highlight is Last Sight Vision, which allows you to see what a creature did moments before dying and would come in handy for an Eberron inquisition-themed adventure.
Undead grafts are very similar to the variant dragon traits in Draconomicon, but just let you add a new ability to a creature instead of exchanging it. Kind of like a template-but-not-really. You can give your big-bad a mummy's eye that allows him to use eye of despair, or an eladrin wizard a lich's brain so that he can recharge one of his spent powers during a fight. It’s simple, elegant, and (most importantly) effective.
Chapter 3 contains a grand total of nine undead lairs, which range from graveyards to the corpse of a dead god. They're all pretty small and could be handy for some map inspiration or just directly dropped into an existing adventure.
Saving the best for last, Chapter 4 is brimming with hordes of new undead to play with, old and new. The crawling claw, several beholders, and the brain in a jar are a few very cool things that make a comeback. There are also new ghosts, ghouls, a golem made out of tombstones, mummies, liches, a creepy kid's skeleton—the list just goes on.
There are also more than a few templates, such as Ascetic of Vecna and Infected Zombie, which brings me to one of the main complaints about the book: the Infected Zombie template lets you infect targets with a disease called zombie plague, but it’s not mentioned in the book anywhere. It’s been a few months since the book’s release, and we’re still waiting for that little tidbit.
This book is very solid. My only nitpick is the quality of some of the art, particularly Kas and Vecna, but the rest of the book more than makes up for it. This is a must-have for all DMs, if just for the new monsters alone.