Is this game all about co-perative play or is it also enjoyable when going solo?

...it better be, because I got a hunch it will be hard to find games in the coming month or two.

I have yet to play co-op and am enjoying the game. 
It's by no means a "must have other people" kind of game.

It's kinda bad SP.

The gameplay is something I see would be quite a lot better with more people, if only because of the chaos that I assume will ensue. 
I've only played it solo so far, but the humor is something that is excellent no matter if you are alone, though the fact that I'm swedish might make it even more funny... 
I think it's one of those games that is better with more people, because of the random chaos, but it's still good even if you play by yourself. 

it's definitely challenging at parts where there's a bunch of enemies and little old you. i spawned those ents whenever i could and when i learned the raise dead and summon elemental spells would use those often to get my back.
 
still really, really fun though.

Well,its like Borderlands its better with more people playing it,but can also be fun solo.

Nothing "wrong" with the game, although the text usually does say "the Wizards traveled to Morgondor". Not that that matters much obviously. 
 
Main problem is just in the difficulty, you have a resurrection spell that you can pop off instantly but with no mates you'd have noone to use it on.

It's too hard for me, I can't get past chapter 3. A ton of big charging dudes keep hitting me in the air like an infinite juggle in a beat-em up. Can't cast anything, can't do anything.

Up until ch5 single player is fun, ch5 is just hell. Between Khan & all the army you fight beforehand I'd be finding it next to impossible without the tree army (from the staff) & time warp. Without those two things I can't see how to get past that level.