Rosemary Jones's debut, CRYPT OF THE MOANING DIAMOND (USA, UK, Canada) is part of The Dungeons series by Wizards of the Coast. Other titles in this series includes Depths of Madness by Erik Scott de Bie, The Howling Delve by Jaleigh Johnson and Stardeep by Bruce R. Cordell. I found this blurb at the author's website:
Once again Tsurlagol has been invaded and now a band of orcs controls the city and the city's stout defenses. Luckily for the citizens of Tsurlagol, the forces of Procampur have come marching to the rescue. Even more luckily (although the proper and extraordinarily stuffy Procampur officers don't know it yet), the Siegebreakers are available to help for a quite reasonable fee.Wizards hosts a sample chapter in a zipfile. The author maintains a MySpace site, including a blog.
The merry band of mercenaries knows all the tricks for overcoming a city's defenses. Except the Siegebreakers just fell into a vast underground ruin, which is being flooded by the river that they unleashed. The waters are rising, the ceilings are collapsing, and every turn reveals a new creature that wants to attack them.
Ivy, the leader of the Siegebreakers, knows that making walls fall down is easy: not being underneath when the walls collapse is the hard part.