<Penned by the skilled hand of Archmage Ansirem Runeweaver>
Necromancy is the study of magic involving the dead. It is highly illegal and should be avoided at all costs. I discuss necromancy here only because it is our obligation to have a basic understanding of the magic employed by our enemies - and make no mistake, any practitioner of necromancy is your enemy. Necromancers and their followers are the enemies of all living things. Their influence must be avoided at all costs.
Necromantic magic has many functions beyond simply raising the dead. Masters of this tainted field of magic can conjure festering diseases, harness the shadows into bolts of incendiary energy, and chill the living with the power of death. Necromancy can also be used to reconstruct the flesh of undead creatures, allowing them to function again even after the foul monsters have been destroyed.
The former archmage Kel'Thuzad is perhaps the most notable example of a modern necromancer. He greatly contributed to the initial spread of the Scourge and the fall of Lordaeron. Now, Kel'Thuzad reigns as a lich from the floating citadel of Naxxramas. His ongoing existence poses an imminent threat to us all.
This book appears in the Legerdemain Lounge, Dalaran (46.9,39.1). Go to the first floor, in the room to the left(west), on the usually empty bookshelf.
The timer for respawns is between 3 and 4 hours. So if you see a comment in Trade chat, or the specific channels such as higherlearning (type /join higherlearning to see it), aim to return in three hours and calculate the respawn period for the book from there.