It is, like most of their work, very much run by the keyboards as the guitars take a back seat. Basically, symphonic black metal with low quality recording (which can be a good thing). If I remember correctly from the last time I listened (a long time ago) they incorperated both screams as well as clean, epic vocals.
Their reliance on keyboards reminds me a lot of emperor, even though there are some major musical differences as well. If you didn't like Aspera Hiems... than you probably will not like this.
If you haven't heard Aspera, then I reccomend you try it out, though preferably without spending any money (not everyone likes it... took me a long while to warm up at all to it). My main bone with them is not really with them, but with the style they helped create, which is the style that such shitty bands as Dimmu (and later emperor) use today (clean as well as screaming vocals, keyboard reliance, slower tempos in some cases)
I am not going to say they are absolutely amazing albums, however in my opinion the first two were a big part of the later black metal era.