This set of tiles features the accessories missing from the other dungeon sets. It includes a moldy green cistern that's eight squares in diameter, prison cells that are two squares wide and four squares deep, smaller cells that are just two squares across, a tomb filled with coffins, a spider web four squares in diameter and a variety of webs spanning columns and corridors. There's also a diamond-shaped storage chamber, barracks, study, filthy living quarters, and a lab.
It's unlikely game masters will need all of these accessories and instead need them for only one or two features. Huge cisterns 40 feet across are rare events in dungeons. Prison cells are certainly useful, but the prisons are all very narrow, which means they may not comfortably fit larger humanoids. Coffins are always useful. I purchased this set to flesh out the lair of an aranea and I consider the spider web tiles (five in total) to be the primary reason to buy this set. The humanoid quarters are useful if that's what you need, but they're very specific – while the storage chamber and barracks can be reached by connecting to a single corridor that makes them compatible with most other dungeon sets, the study, filthy quarters, and lab are open rooms that are not self-contained.
This set has limited utility. Buy it for the web, the coffins, and the prisons, but it's unlikely you'll use the other details.