The books follow Jean and friends through adventures all over the Solar System, from Mars to Earth to Saturn and many points between. Jean is a self-described master thief, and so it's not surprising that a lot of the story revolves around pilfering stuff from under the noses of its owners. The larger plot involves the fate of society in the entire system, so it isn't just about stealing shiny objects, though there's plenty of that in service of the end goals. And there's no shortage of action along the way, either. Each of the books has multiple passages that read like descriptions of the craziest special effects in sci-fi movie battle scenes, and I mean that as a compliment...it's fun to envision actually seeing all of what Rajaniemi has written.
Through all this, Rajaniemi doesn't do a lot of hand-holding. New terms get thrown at the reader with minimal explanation. There's plenty of weird happenings that don't make sense until much later when the reader has more information. As I said earlier, you have to put up with quite a bit of uncertainty. But I felt that by the end of each book, Rajaniemi had done a reasonable job of clarifying what had happened and why.
As far as the science aspect of sci-fi goes, Rajaniemi has gone far enough out into the future that much of what he describes seems like magic. Clarke's third law applies here: "Any sufficiently advanced technology is indistinguishable from magic." There's a good amount of explanation scattered throughout the trilogy, much of it involving quantum effects or nanotech, which to my layperson's mind seems plausible. And Rajaniemi certainly does a fine job with the descriptions, unsurprising since he has a doctorate in physics. But it's so far ahead of anything that exists in today's world that there's really no way to know how feasible any of it is, so it's easiest to just suspend disbelief and accept the premise without worrying about how it works.
My favorite part of the world building isn't the technology anyhow, but rather the social orders. The Oubliette is a whole society built around taking privacy to the extreme. Innumerable mind-copies of a few original Founders created the Sobornost society made up almost entirely of themselves. The few who still live on Earth fight against corruption by rogue "wildcode" technology that tries to corrupt mind and body. And my personal favorite, the zoku collective that gamifies everything, using points and levels and "entanglement" bonding to both keep score and organize their efforts. Given the changes wrought by technology and shifting environments, I thought the social and political structures that Rajaniemi describes are plausible and certainly the ideas are thought-provoking.
If my previous warnings about complexity and uncertainty haven't turned you off already, then you're probably going to enjoy the trilogy. I certainly did.
