A. A. Attanasio's books contain layer upon layer of subtext. He's among the most intellectual of authors, without being in any way pretentious. This is a writer who uses obscure words not to show off, but because they're the right words.
Solis is an adventure story, a chase of bad guys after good guys. And it's a cautionary tale about cryonic preservation. And a consideration of what it means to be dead, to be property, to be human. Its main theme is right there in the title - a search for solace, and ultimately satisfaction.
Attanasio is almost always a smooth, highly visual writer. His concepts wanders toward the mystical, while his characters are down-to-earth regular folks. His prose tends toward the dense and philosophical. It's always perfectly readable, but always leaves me thinking there's some higher meaning floating just out of reach, that Attanasio is just slightly (or greatly) smarter than I am. Yet it's not frustrating or offputting. Attanasio is simply one of the very few writers who've managed the art of intelligent writing.
Despite his obvious skill, Attanasio seldom makes the leap from very good to extraordinary, from "that was a fun and mentally challenging story" to "I will remember that story and think back on it for years". His concepts are perhaps on such a high level that they don't resonate easily with our needs-focused brains. That rule applies to Solis as well. The characters are likeable; their quest is urgent and comprehensible; they react like regular people. But the broader concepts they deal with are a step or two removed from everyday existence; they're intriguing, but hard to internalize, and they never quite reduced themselves to concrete conclusions. It suggests Attanasio has found a balance that makes the reader think, rather than just accepting clever aphorisms, but it also makes the book harder to catalog. Re-reading Solis after many years, my mind offered "That's the book about ... Well, it's about ... There was something... It was pretty good."
It is pretty good. It's about quite a lot of things. If you let it, it will make you think. If you're looking for simple adventure, that's in here. Mostly, though, it works, as much Attanasio writing does, as a sort of journal by someone who's out there searching for the same existential answers the rest of us are, but writing it down much, much better.