After the strong opening in Spin and the someone meh followup with Axis, I wasn’t expecting particularly much from Vortex. Consider me pleasantly surprised.
Getting back to the huge events and big timespans of Spin, Vortex takes place ten thousand years after Axis, after the Temporal Arch discovered towards the end of that book ends its next cycle. Two of Axis’ main characters (Turn and Isaac) are dumped out / recreated and picked up by a island sized ship that has been floating through arch after arch through the Eight Worlds (apparently the arches connecting Earth to Equatoria connect through several other worlds and finally end at Mars, which is a neat concept).
The far future society is interesting, as is the ruined Earth (global warming is bad). In the far future, societies seem to resolve around linked communities, either linking the thoughts of emotions of a community. The island they end up on is one of the latter, which has both its strengths but also a fair number of complexities, both of which I thought Vortex did an interesting job of exploring.
On the other hand, there is actually a second story line interwoven into Vortex, revealing the ten thousand year future as a story written by a possible mental health patient. Honestly, I’m not sure why this storyline is here; I thought those parts weren’t nearly as interesting (we’ve already seen that part of the timeline after the Spin) and could have been left out. They did set up an interesting possibility for the very conclusion, but that could have done without as well.
We also do learn more about the Hypotheticals (not so hypothetical any more…), which remains a neat concept, even if one that doesn’t always make terribly much sense (how do they communicate?).
Overall, my previous point from Axis remains: If you read Axis, read all three. Vortex is a solid conclusion and an interesting book on its own merits. If you’re more pressed for time, you can read only Spin and be well off.