From the publisher's website:
"About"? "About"? This module is not "about" anything. It is the purest location-based module I've ever seen. Not one word is about anything other than the titular Lurid Sac. That's your location.
Confused? Think about where Han Solo flew the Millennium Falcon in The Empire Strikes Back. Or, more precisely, into what he flew it. The Lurid Sac is freaking alive! The whole damn dungeon is one giant monster. And what a monster! The Lurid Sac is nothing less than the most amazing monster ever published for D&D. I can't tell you how cool the whole thing is. Summaries fail Dreams of the Lurid Sac, which is tightly and precisely written. It's weird that Paul was able to use such exacting language to describe something so fantastic, so outre, so crazy. He has raised the bar with this one. I think it one of the single best (and certainly one of the most imaginative) modules I've ever seen.