(I actually like this poster better as a work of art, but it's actually a terrible advert for the film)
It's a bit of a filmmaker's film. There's a lot of playing off crime and action movie clichés and the plot is literally about a Marty (Colin Farrell), a screenwriter who's struggling to write a script titled "Seven Psychopaths". They are literally writing the movie in the movie. The meat of it though lies in that, while struggling with the script, Marty inadvertently ends up involved in a friend's (Sam Rockwell) business venture. And when I say "business venture", I mean the business of kidnapping dogs in LA and returning them when a reward is offered. Of course, these dognapping psychopaths eventually run afoul of another psychopath when they steal the beloved shihtzu of a mafia boss (Woody Harrelson) and he ain't paying to get it back.
Packed with bloody punchlines and genuinely messed up people (who may or may not be psychopaths) the film finds a lot of its wit in the darker realms of comedy. It gets a little goofy at times but the performances really sell it: Sam Rockwell and Colin Farrell make a wonderful odd couple, with the former playing the manic go-getter and the latter filling the cynical, Irish writer who (stereotypically) has a drinking problem. With Christopher Walken by their side and a host side characters who only occasionally clock how crazy the main cast are, the ensemble works to hit every black beat at the heart of the film.
A tight script that ends with some emotional moments to back up the laughs, Seven Psychopaths doesn't quite feel as tight and neat as Mcdonagh's last foray onto the big screen but it most certainly works. In Bruges was a very tight story involving some three very well written characters. But Seven Psychopaths is more of a smorgasbord of interesting characters with a slightly less coherent reason for them all to run into each other, but it works well enough, especially in the context of the satirical points the movie makes about movie plots anyway.
You don't have to be a movie nerd to appreciate the hilarity of Psychopaths, but those who are will enjoy it that little bit more.