Ulver are so varied it really depends what you're into
I love their first 3 albums immensly
Bergtatt is great, epic, melancholic BM
Kveldsjanger is a folk album, very melancholic, i guess my personal favourite
Natten's Madgrial-very raw BM
Themes...-mix of electronic and rock/metal. I have a hard time getting into this one. I haven't bought any of their material after this release since i'm not overly fond of electronic music however i hear Lycanthropic Themes is more ambient and therefore it interests me more.