When I first listened to this album, I was expecting to be bored in a few minutes. Instead, I listened to the entire thing straight through - it's that compelling.
Orthrelm take all the sound and fury of metal and couple it to a highly repetitive, minimalist aesthetic somewhat reminiscent of Philip Glass or Steve Reich's classical music. This is a fairly unique concept - I, for one, have never heard anything much like this album. It's wildly different from slow-building, strung-out 'stoner rock' like Earth or Sunn O))), as it moves suddenly between series of repeated, intense figures (call them riffs, I guess) that are played at blinding speed. Though a single riff can repeat for a while - up to six or seven minutes - it hardly ever gets old: each is complex enough to withstand that sort of repetition. Of course, there is slight variation in the way each riff is played, as well.
The guitar and drumming is insane - its speed and precision over such an extended period is unbelievable.
This album is certainly not for everyone. However, I wouldn't say you have to be a metal fan to appreciate it (my own knowledge of metal is quite limited). It's good to have some background in experimental or minimalist music, though - a tolerance for dissonance and a willingness to listen closely.