Albums:
Orchid is a classic
Morningrise is cool, but the production kinda sucks
My Arms, Your Hearse is very heavy (the song Demon of the Fall IS a must have)
Still Life is their best (IMO)
Blackwater Park is a must have (and easy to get into)
Deliverance is super heavy
Damnation is very cool but completely mellow
So I'd say; start with Blackwater Park, if you're completely into that one, buy Still Life and the rest is up to you.
BTW, I asked Mikael (the singer/guitar player) the same question three years ago. I only had Blackwater Park back then, and he recomended me Still Life. So there you are.
