Awesome underrated music.
Like most video-game music it has no vocals, instead the music is very creative and loaded with "feel".
What you have here is essentially mysic of three generas.
You have the Harkonnen music which is hateful and malicious, with lots of screaming guitars and a march like rythm.
You have the Atreides music which conveys righteousness and nesssecary war with a much kinder but still warlike tone... listen to some of it and i tink you'll understand.
Lastly you have the Ordos music, which is very techno-ish, with strange tunes and tempo.
On top of that are a few songs that are just plain moody but doesn't tie to a specific faction, i won't even try to explain 'cause my words wont do 'em justice.
Were i to pick a favourite song from this ablum it would be: Tribute to Evil, closely followed by Harkonnen Force.
If you're unsure whether you'll like it, download assembling the troops.mp3 it pretty mouch sums up all three factions in turn, starting with the Atreides, then going over to the thechno-ish Ordos, and lastly a milder variety of Harkonnen.
I also reccomend you look up other works by Frank Klepacki, Jarrid Mendelson and David Arkenstone
As they are all really great composers in general.