As the title really, is the multiplayer a full co-op run through of the single player game or is it a death match / arena type of thing?

Thanks in advance

Co-op run of the entire game. More details on their site.

You could play Coop, or PVP. It is up to the host.

For PVP it's not arena style, it just means anyone who joins in can slaughter you if they come across you in the game world, BUT they cannot take your gear.

Coop is based on two things, instanced loot drops are not shared meaning that you will each have loot to pick up, if it's not instanced then even though you made the kill the loot can be stolen by anyone who is with you which happened to me, and really ticked me off to no end.

It still technically can happen as any item you pickup up due to move to cursor preferentially doing so instead of attacking will instead drop the item if your inventory is full.
The game treats this as an item discard and makes it visible to anyone your with allowing them to click to pick up.
It's annoying trying to figure out who gets what after a mob scene playing with a friend because you have to go back and decide to divvy it up which takes effort and otherwise breaks up the intense hack and slash action.

Ooh, OOH OOOHHHH!!!

Time to get a cronie to grab the game & start trolling each other all over again.
It`ll be like good old Magicka times >;)

If you, or anyone, is looking for a co-op buddy pm me. I've noticed that there are few people hosting games on GOG and those that do sometimes keep it locked.

Yeah i run mine open too.
I think a lot of people are running it locked so they don't have characters that are to high in level pop in at in-opportune times.
The developers made a poor decision to disallow power leveling by capping the differential between levels that grant experience to i think about 10.
If your in a game partied up with someone of 10 levels higher you get like no experience apparently.
However the game is still fun if your character is fairly high in level (say 30) and you like a bit of a varied challenge going round with a level 50 odd buddy once you stop caring about leveling and focus more on item drops.