Rather a neat and at times claustrophobic adventure that takes some of the common tropes of fantasy adventuring and twists them into something new. How many times have you started a game with a bunch of well-armed strangers meeting one another in an alehouse and setting off to risk life and limb together with scant reason for doing so? This adventure starts with a bunch of well-armed strangers meeting in an alehouse but turns everything on its head to meld them into a real party with reasons for sticking together... and as such makes an idea campaign-starter as well as an interesting adventure in its own right.
The inn in which the adventure starts is well-detailed with a fair few interesting locals for the characters to interact with, and it is a prime opportunity to mix in rumours and seeds of any adventures that you have planned for later on in your campaign. Much of the suggested interaction is designed to facilitate character introductions - someone who asks loads of questions about their pasts and the like - which also fits with the campaign starter model.
And then events take an unusual turn... the inn subsides in a massive landslip that leaves the characters trapped underground, apparently the only survivors, and have to find their way out through many dangers to the surface again. The actual collapse could be better described (just imagine an earthquake strong enough to do structural damage), although the 'characters waking up afterwards' is nicely done. A good dungeon crawl ensues.
Everything is well-described and there is a clear map for the DM. Even better, there's a page-full of suggestions for further adventures based on what the party find in the depths as well as a selection of wandering monsters to complement the ones situated permanently in the various subterranean chambers they explore. There are also a collection of traps and some quite unusual treasures that you may distribute as you see fit. For the botanically-inclined, there is a section of 'random flora' that you can place as appropriate - some of them are quite interesting - and there is also a write up of a minor deity.... and the full stat blocks for everyone/thing that will be encountered.
As a starting adventure, this one has it all. Recommended.