How? Found at the library.
What? Even though there is a Buffy RPG (by the semi-late Eden Studios), I think is probably the biggest RPG game in that space: you are monster hunters in a world that doesn't know about monsters. This is a Powered by the Apocalypse game, which is to say, characters are built on playbooks (which are combinations of concepts and moves) and you roll 2d6 + a modifier from your character.
The game is meant to accommodate really anything you could find in Buffy/Angel or Supernatural, so the character types are Chosen (Buffy), Crooked, Divine, Expert (Giles, Willow the hacker?), the Flake (Cordelia), Initiate, Monstrous (Angel, Spike), Mundane (Xander), the Professional (Riley), Spell-slinger (Willow), Spooky, the Wronged. It's a reasonable list, right? And the fact that the book is littered with references to Buffy, etc., is just a marker of how determined they are to do genre-emulation.
But wait, the game is complete in one book, so this book isn't just player info, but also GM info on how to run a game, which includes a breakdown of monster types and motivations, which I have to include:
• Beast (to run wild, destroying and killing)
• Breeder (to give birth to, bring forth, or create evil)
• Collector (to steal specific sorts of things)
• Destroyer (to bring about the end of the world)
• Devourer (to consume people)
• Executioner (to punish the guilty)
• Parasite (to infest, control and devour)
• Queen (to possess and control)
• Sorcerer (to usurp unnatural power)
• Tempter (to tempt people into evil deeds)
• Torturer (to hurt and terrify)
• Trickster (to create chaos)
And the book also includes minion types:
• Assassin (to kill the hunters)
• Brute (to intimidate and attack)
• Cultist (to save their own skin at any cost)
• Guardian (to bar a way or protect something)
• Right hand (to back up the monster)
• Plague (to swarm and destroy)
• Renfield (to push victims towards the monster)
• Scout (to stalk, watch, and report)
• Thief (to steal and deliver to the monster)
• Traitor (to betray people)
Hmmm, that's a lot of types with a lot of good inspiration, but what exactly is the system here for this categorization? How, in fact, does describing a minion as a Renfield help at the table?
And! Of course players have moves to make (like "assess a situation" and "kick ass" -- which seem pretty commonly used in a game about investigating and fighting monsters), but did you know GMs also have moves? Things like "inflict harm, as established" and "tell the possible consequences and ask if they want to go ahead"; and monsters have moves like "appear suddenly" and "destroy something"; and the book even describes moves for minions -- "give chase" -- and bystanders -- "go off alone".
Yeah, so? (Alternate title for this section: "Why did I just list all of that?") I think this game seems perfectly fun for the genre its emulating (monster hunters in a monster-filled but otherwise normal world). And Apocalypse-powered games are meant to be fiction-first or fiction-forward: you don't look at your character sheet and then decide what power to use, you just describe your character's action, and then find one of the broad moves that describe that. (That's the theory at least. I think that flow breaks down a bit the more specialized and powerful the characters get.)
And while that "fiction-first" attitude may explain why monsters have moves like "put someone in trouble," I am reminded of Laurence Olivier's semi-ironic advice to method-acting Dustin Hoffman: "Why don't you just try acting?" I suppose this book is meant to be friendly to new players and GMs -- people who like Supernatural but have never played a game before. (Even though, ahem, there is a Supernatural game from 2009 by Margaret Weis Productions.) But reading it, it almost feels more there's too much here, especially when the book otherwise has a lot of examples and advice re: taking an episode from the show you like and just re-using/-skinning it.