I second that. You can't go wrong with Monumension - you'll especially like it if you are into complex metal...and I guess you are, otherwise you wouldn't be here. Mardraum is even more complex than Monumension, or should I say more chaotic? Monumension is easier to get into, it has a kind of structure, that's maybe because it's a concept album.
If you are into fast and straight extreme metal you'll love Blodhemn, it's the opposite of the 2 last albums - only straight easy-structured metal, but played tight as fuck.