I really enjoyed 30 days of night. But, mainly looking for a non-superhero book. Something dark and definitely not anime/manga.
Depends what you mean by 'dark'.
'Fell' by Warren Ellis is a good read, if you've not read that
'Phonogram' is a bit wierd, but probably worth a look
and while you said no super hero stuff, if you've never read 'Sleeper' I highly recommend it
100 Bullets would be a good start for something dark.
I'm not a superhero fan either but I can't recommend Watchmen highly enough. It's about a lot more than just superhero guys and in fact only one of the characters actually has powers.
Peace
Duckman
Fell is excellent and its the same artist from 30 days of night.
I can see jesse really really liking Midnight Nation. Strong recommendation there.
Night Mary was a good dark graphic ill come back with a better list
Realized I forgot to add 'Girls' by the Luna Brothers to my list