Concept: “Deep in the jungle, far from civilized lands, lies an ancient temple dedicated to a long forgotten god.” 
Content: A “4th level adventure” of alien gods, blood sacrifice, and ziggurats.
Writing: A heavy science fantasy/weird fiction setting with loose references to elements of Preclassic/Classic Mesoamerican civilization. 
Art/design: Dark and forbidding page illustrations of strange aliens and ancient machinery highlight an effective single-column layout.
Usability: Organized for reference over multiple sessions. Occasional generalized OSR rules reference.