From publisher blurb:
"In the middle of the ocean, far from any land, lies an area known as the Sunken Jungle. From a distance this region appears to be a low, forested island, but it quickly becomes clear that it is something entirely unique."
The purpose of these books is to help DMs put together an interesting encounter in a short time. Each Adventure Keys release does this by starting with a unique location that can be inserted seamlessly into an existing world with little or no modification. They are modular, with many options and variants available so that the DM can customize it to suit their needs.
There are six sections that include the Location, Hooks & Goals, Characters, Trappings, Threats, and Changes. All but the first have multiple options each, and since the DM isn’t limited to using only one option, the variations available are quite numerous. Sections can be used or ignored at the DM’s discretion, or even modified based on the situation or to scale its Challenge Rating.
The options are deliberately non-specific for ease of use. The DM can include them as they are, combine them, or use them for inspiration to create an entirely new options.