From the back of the book:
All of the 14 lethal levels in the Vault of Splintered Souls embrace their own unique elements while intertwining into a beautiful delve that embodies the themes the fantastic patrons of 'EN5ider wanted to see most, ultimately creating an adventure that your group is going to be talking about decades from now. Within this tome of terror are countless hours of combat, exploration, and puzzle-solving throughout some of the deadliest ruins below Mal Takkar--a trek that has already caught souls innumerable in its immortal embrace.
22 monsters from the lowly CR 0 bloodnit to the impressive CR 15 titan's gate gladiator!
4 magic items, several new pieces of mundane equipment, and new diseases.
Player handouts for puzzle-solving.
An innovative system for rewarding new levels, powers, and lore about Mal Takkar the further down the adventurers get.