Usually, I write reviews that detail the good and bad of a product. I have to do things differently this time around, because this sourcebook is ALL good. Let me tell you why:
FOR THE DMs: The book details pretty much everything you ever needed to know about running undead monsters in your campaign, and then some. The material is extremely well-organized and concise, allowing it to be used readily and requiring little, if any, prior research on the part of a DM to incorporate both "new" and "traditional" undead monsters into the campaign. Updated definitions of abilities and traits are included (even incorporating descriptive material from the Monster Manuals through MM3). Without getting too boring, details are given on the methods and motivations of all of the "traditional" undead types (skeleton, zombie, ghoul, ghast, shadow, wraith, spectre, ghost, mummy, mohrg, vampire, and lich), with information given on creation methods above and beyond the typical myths surrounding these monsters and the mundane "game mechanic" procreation abilities possessed by some of them -- all excellent fodder for creating new adventure hooks or plotlines to jazz up any "haunted house" adventure. In addition, a number of ready-to-use horrors and their backstories occupy a section of the book all to themselves, just waiting for you to pick up and run with them. The latter portions of the book detail more new undead creatures -- fair warning: while there is, at least, no nudity, the illustrations in the New Monsters section makes much of the artwork from the Book of Vile Darkness seem tame.
FOR THE PLAYERS: For those of you out there that enjoy running uniquely interesting campaigns with a twist, there are rules and options presented for playing an undead horror as a PC. Setting up and running an undead character using this book is slightly more involved than running undead creatures as monsters, but the superlative organization and breakdown of information makes this a much more simple task than one might expect. In the same vein as the "Savage Species" sourcebook, Libris Mortis presents the "standard" undead creatures from the Monster Manual as character classes, detailing progression and ability acquisition from 1st level on upward. Since all of the "basic" undead monsters are covered, it's not difficult to extrapolate your own progression for less mundane undead creatures should you desire to expand your options. I was particularly impressed with how smoothly and effectively the character rules presented take all of the best concepts about the old 2nd edition "Requiem" campaign from Ravenloft and simplifies them in 3.5 edition standards.
FOR BOTH: A number of prestige classes (mostly for villains, but with a few foes of the walking dead thrown in) appear here, including updated revisions of a number of prestige classes that originally appeared in the "Defenders of the Faith," "Tome & Blood," and other sourcebooks (including the True Necromancer, the Master of Shrouds, and the Pale Master, among others). A respectably sizeable feats section caters to players and DMs alike, with a plethora of options available for both undead creatures and those that hunt them. With the New Spells and Magic Items sections comparable in size and variety to those provided by the "Complete Divine" sourcebook, there literally is a little something for everyone in the book.