Arkham Horror is an excellent board game based on the Cuthulu mythos world of HP Lovecraft.  

It can be played solo, or with a number of players (we played with 4, but it can accomodate up to 8 with ease).  The game is designed so that you play against the game itself, no one takes the part of the monsters that appear.  

Encounters are random, generated by drawing cards as part of your movement.  Game mechanics are simple and self explanatory as you progress with combat driven by D6 roles. 
 
You have to check your characters sanity (mental strength) before you take on monsters.  Characters can be killed by the monsters, but with careful play, you can get fixed both mentally and physically before this happens.  Just like in a Cuthulu story you are likely to go insane before dying.

The board looks terrific, as do all the various cards.  All the artwork is good.
 
The designers have gone out of their way to give it the feel of a 1930s Cuthulu story, with gangsters, dilenttantes and ex service men racing against time to save the world from being consumed by a dark menace from beyond space.

In the game we played, we were fighting against Glaaki.  He's a local monster, for local people (being based in the west mids).
 
We had 4 players, controlling 8 characters.  Mark whittle spent most of his time collecting Mythos tomes (despite me urging him to burn them), and getting trapped in the historical society by people trying to tell him their life stories.  James Moore controlled a nun (she was a bit hard- but ended up cursed by the forces of darkness and going insane).  The other 2 players were Alex Hickman, and myself.  I have to admit I probably could have played more seriously, but I was having far too much fun setting fire to stuff with a flamethrower while getting lost in time and space, if I was'nt looking of statues of myself in the future or hiding in the botanical gardens from dark young of shub-niggurath.

We managed to defeat the forces of evil, although at some stages if was touch and go, with gateways to other dimensions were opening faster than we could shut them down, allowing hordes of various ichor covered villains to defile the streets of Arkham. 
 
All in all I would give this this game a 10 out of 10 and look forward to playing it again.