Well, Chad Underkoffler has done it again, and this time he's managed to keep a good, consistent tone.
This is a PDF download from SJG's new e23 store, only available in "virtual" form, as far as I know.
What is it? Well, it outlines the "Temple of the Lost Gods". But it's not just a dungeon crawl, it's an entire campaign setting through the lens of the Temple: Not only does the supplement outline the history of the Temple, with adventure seeds for every period, but it outlines an entire generic fantasy kingdom, from rise to fall. I say generic, but this supplement is actually packed with flavor.
And not only that, but while it's designed for GURPS, you don't need GURPS to play. It's designed for use with GURPS Lite, which you can get for free, with all the additional material needed to play. And if you already have GURPS, the additional material isn't that much wasted space: Some of the material is new, and the majority of the material is system-independent, which makes this supplement great if you'd rather use another system besides GURPS Lite.
So, what do you get? Well, in detail:
Chapter 1 is the history of the Temple, but it's more than that. It gives the wonderful cosmology of the Lost Gods, which is one of the nicest self-contained little cosmologies I've seen in a RPG. In essence, there was a war in Heaven, and several gods were cast out, becoming stars in the night sky. Other gods took over their portfolio, but they don't do as good a job as the original gods, and thus all suffering, pain, and evil that exists are explained. The Temple seeks to bring back the Lost Gods, and restore the world to a golden age. Not only is this cosmology interesting and realistic, but it still leaves room for the Lost Gods to be evil, if the GM wants to wint things that way.
The history is divided up into Phases, which outlines the fortunes of the Temple from its founding after a brush with the Lost God of Speed, to its connection to the royal family, to the Madness Plague (spread by magic), to the final downfall of the kingdom the Temple is in. Each Phase gives more than enough detail for adventures during that era, succinctly, and a handful of excellent adventure seeds, tho some of the seeds tend to assume the PCs are sidekicks to major NPCs, a minor failing that is mended in a later chapter.
Chapter 2 outlines the Temple as it stands at the end of the timeline, after the Last Priest cuts the Temple off from the outside world to concentrate on bringing back the Lost Gods. This is sort of a dungeon crawl, but it's packed full of GM options -- the GM decides what the inhabitents of the temple have been doing -- and is chock full of the results of interesting magickal experimentation, including some strange chimera.
Chapter 3 gives a dizzying array of campaign options for the Temple, mixing it from "ordinary" fantasy to the modern day (including an interesting Hellboy spin) to science fiction. Here, the author examines whether or not the Lost Gods are as benevolent (or real) as the religion claims, and the possibility of the PCs messing with the timeline, giving all sorts of options, including the highly flexible "the PCs replace the major NPCs" option.
The Appendix contains all the additional rules needed to run the game, including a neat little magic system (a bit more flexible yet more heirarchy-oriented than the standard GURPS magic system) and a list of the Lost Gods.
Frankly, if you're not inspired after reading this supplement, you're dead. Chapter 1 is worth the price of admission alone: I cannot convey how tightly written and useful that chapter in, chock full of more flavor than I can convey. If you've got an extra few bucks, this supplement is serious bang for the buck.

