This is a systemless adventure, suitable for any modern or near-modern game system in which the supernatural is real (the author suggests Call of Cthulhu, D20 Modern or the World of Darkness as examples).
The core of the story involves an amazing archaeological discovery and a bunch of travellers caught in a snowstorm. The introduction/backstory explains what is really going on and the nature of the threat whcih the travellers will have to counter. Unless you decide to use this as an event within an ongoing campaign, it is suggested that the travellers should be a quite disparate lot, each one with his own reasons for being in the area of the Thirteen Pines township and just caught up together in ongoing events.
The opening scene is dramatic, with the characters - who may at this point not know one another, unless you are running an established party - driving through atrocious snowy conditions towards Thirteen Pines. An abandoned vehicle kicks off the action and the game is afoot...
Once the initial scene has played out, the rest of the scenario is quite freeform. There are locations to investigate and a few people to talk to as the characters try to piece together what is going on. An 'adventure flow' is suggested to help you keep matters on track, but it is not rigid allowing plenty of scope for a charater-led game.
Everything is scary, snowy and almost claustrophobic with the travellers and a few other people trapped in town. Phone lines and cell reception is out, but the power is on at least for the moment... but where are most of the townsfolk? Descriptions are atmospheric and you should have little difficulty in bringing the scene to life in the minds of your players. The scenario will be most effective if run at a brisk pace, and would probably be suitable for a convention or other single-session game.
The whole adventure is well-presented with apposite illustrations, a plan of the town; and only a few minor typos which jar but do not render the text unintelligible. Naturally as a generic scenario, you will have to apply appropriate statistics from your chosen ruleset, but otherwise it is good to go... an adventure you and your players will remember for years to come.