It’s been a while since I’ve read a really original science fiction book. Recursion is definitely that; it manages to introduce novel and challenging storytelling devices without the typical hand-wavey scientific jargon. Its central conceit (no spoilers here) is about humans, not technology. The key questions it raises are more about the mind, not robots or space or AI.
The plot gets twisted into knots, making it a bit hard to fully engage with at times. It’s no Primer, but it’s just challenging enough to require more attention than average pop sci-fi. But impressively, the whole thing stands up to scrutiny; no obvious contradictions or conveniently-applied plot armor. Quite an accomplishment, given the scope of the story.
Definitely read if you liked Three Body Problem and Exhalation.