From the Pacesetter Games and Simulations website:
Thunder in the Deep is the second of a five module series that expands the The Dwarven Glory adventure kit, originally produced by Wee Warriors. Each module focuses on one of the five “levels” of the mine, becoming successively more difficult.
The text on the back of the book appears to relate to a different adventure, V11 Curse of the Violators, which was the first Pacesetter release expanding The Dwarven Glory. Internal pages are also headed with the title Curse of the Violators.