@tsrono It's hard to pick just one!
I particularly enjoy the first 4 albums: Vakio, Kulma, A, and Aaltopiiri, with A being my favorite since it was my first.
I like Kesto as well because it covers a lot of ground (it's just over 4 hours long with the last track taking up its own disc) and I'd highly recommend it to newcomers.
I think Atomiin Paluu is a great example of their later work as well.
@emenel @tsrono Yeah, they're up at the top of my list too. I had a similar experience when first hearing them.
I got A circa 2000 and don't quite remember where I had heard about them. I was already heavily into Aphex, Autechre, Squarepusher, etc. at the time but hearing that album was the first time I had really encountered such minimalism that was so powerful. The only other thing I could connect it to at the time was Selected Ambient Works Vol. II I guess. I was immediately hooked.