Overview
Monster of the Week (MOTW) is an urban fantasy-horror tabletop role-playing game developed by Michael Sands. It was first published in 2012, and a revised edition was published by Evil Hat Productions in 2015. The entire theme of the game is heavily inspired by TV shows like Buffy, Supernatural, X-Files, Fringe and many others.
The system it directly evolved from is
Apocalypse World (2010)
Description
Players in the MOTW system take on the role of monster hunters. Capable of dealing with most creatures that might get in their way. Using skills to solve mysteries, track monsters and eventually defeat them.
System Overview & Key Features
Powered by the Apocalypse Engine (2d6)
Players roll two six-sided dice (2d6) when performing actions, adding relevant character modifiers to the result. Rolling a 10 or higher is considered a success. 7-9 is a partial success, which will also carry some added consequences. Getting a 6 or lower means failure - you have not succeeded in whatever you attempted and dire consequences are soon to follow.
Basic and Playbook Moves
Game mechanics are categorized into discrete actions called "Moves." Basic Moves are universally available to all characters and cover common actions such as "Investigate a Mystery," "Kick Some Ass," or "Act Under Pressure." Playbook Moves are exclusive, specialized abilities granted by a character's chosen Playbook, allowing them to manipulate the narrative or game mechanics in unique ways.
Finite Luck Points
Each character possesses a limited track of Luck points. A player may permanently expend a point of Luck to retroactively alter a dice roll to a 12 (a complete success) or to entirely negate a single instance of sustained damage. Luck is a resource the players have to keep an eye on. Using too much can get you out of trouble, but if you don't have it when you need it most - trouble awaits.
Harm and Exploiting Weaknesses
Physical trauma is tracked using a short monitor called "Harm." Player characters and adversaries possess low thresholds for sustaining Harm, making direct combat inherently dangerous. To successfully defeat a primary antagonist, players are mechanically required to investigate and utilize the creature's specific weakness, as standard physical attacks are often insufficient to achieve a permanent victory.
The Mystery Countdown
To structure a gameplay session, the Keeper utilizes a tool called the Countdown. This is a chronological timeline detailing the sequence of events that will occur if the player characters fail to intervene. The Countdown is divided into escalating phases, ending with a catastrophic event. It serves to govern the pacing of the investigation and provide a sense of urgency.
Additional links
evilhat.com 
https://evilhat.com - Official Evil Hat Productions website
genericgames.co.nz https://genericgames.co.nz - Official home of Michael Sands and the original game files