From the back cover:
"Ages of Buried Evil
The Bonegarden is a small nation ruled by the dead, a circular cemetery 1 mile in diameter, surrounded by a magical containment field that keeps its denizens from spilling into the innocent world beyond. Within the gate lies one of the true blights of the Domain of Hawkmoon, an immense graveyard that serves as the prison for the doomed spirits of thousands of history's most awful criminals. Those inside are determined to escape, and one of them may have found a way...
An Endless Forum of Adventure
The cemetery is a self-contained battlefield that abounds with undead of types the heroes have never seen, each with its own special plan for escaping its eternal confinement. The Bonegarden contains dozens of new spells, feats, monsters, and magic items. All the action takes place inside a mile-wide arena where the dead are the majority and the living are hunted like wild game. The heroes have come to the cemetery in search of adventure. The only question is... can they get out?"