This note contains spoilers for the book.

 

Believe me, spoilers. Definitely. Yes, spoilers.

This starts out with two parallel stories.

In one, entities (including some that are DNA-derived) learn that a meteor with fossil DNA in it has been found by the Aloof inhabiting the galactic bulge, and they have taken the unthinkable step of sending out a message about it. Our protagonists have been looking for adventure (in a far trans-human future where most people run in computers primarily, and travel by data transmission is possible, though still limited by light speed), and two of them go into the bulge. They're brought to the meteor, and they start studying it and tracking it back.

They eventually find where it came from, in a system disrupted by recent stellar events. They find the remains of a primitive spacecraft, and they find micro organisms ancestral to what was in the meteor.

They keep tracking things, from star to star, and the Aloof support them. They find an "Ark", a stone habitat orbiting a neutron star inhabited by intelligent creatures related to the meteor DNA. They're heavily engineered, and they've been there for 50 million years or some such. Which is doing really well in the unstable galactic bulge.

Meanwhile, in the other story line, we're on an ark and our protagonist is one of the inhabitants. She is recruited out of her work crew to become a theoretical physicist, because another individual has started to understand how their world works, and sees possible dangers and is looking for possible solutions.

They have to discover relativistic physics from scratch, because they're in an environment where it matters. But they do, and even learn how to navigate their ark around a bit (and dodge the Wanderer which would otherwise have killed them all).

As things get more and more dangerous and critical, the tension mounts. And I, of course, am waiting for the trans-humans to meet the physicists. And it doesn't happen—in the end it becomes clear (world-shaking events in one ark don't happen on the other) that in fact they've been on different arks all along.

I'm not sure I've EVER been this furious at a book. That's just goddamned vile CHEATING. It's a low, cheap, trick. There can be no possible excuse for it. I'm thoroughly disgusted with Greg Egan at the moment.