It's in a genre new to me, called post-rock. I discovered it in the way that I often discover new music: by following Amazon recommendations. Somehow I got to guitar-based instrumental post-rock band (er, guy, actually) Lanterna, and from there to here. The genre features traditional rock instruments (your guitar/bass/drums combo) used in non-traditional song formats. It's less electronic than my usual listening, since it tends to have live drummers and no synthesizers.
I also bought a couple of records by Tristeza after sampling on the iTunes Music Store. That's sort of my new general strategy: discover via Amazon. Listen to previews on ITMS. Buy a track or two if I am tantalized by the previews. Buy the CD if I like the track enough.