Their music can be described as "Futurepop", which probably doesn't help you at all. It uses elements of uplifting trance, industrial/EBM, and synthpop.
Basically, sweet hard techno-esque music with dark, epic lyrics over it.
As for song recommendations, I'll list them by album:
Advance & Follow: Frika
Praise the Fallen: Joy, Honour, Solitary
Empires: Kingdom, Rubicon, Standing, Legion, Darkangel
Burning Empires: Further
Futureperfect: Epicenter, Genesis, Beloved
Matter + Form: Chrome, Arena, Homeward, Perpetual
Judgement: Furthest Star, Testament, Nemesis, Illusion
Empires and Futureperfect are probably their best. Praise the Fallen and Advance & Follow have a fairly large reliance on sampling and non-lyrical tracks, and Matter + Form and Judgement seem to have come back to the same kind of pattern (on both albums, there are 5 tracks {out of 11 and 10} that contain no lyrics). Which is a shame, because honestly every "actual" song they've put out has merit.
Also, if you like VNV Nation, you may also like Assemblage 23, Seabound, and Neuroticfish