By Greg Egan
Every journey is the search for an end.
Humanity has become several distinct lifeforms. One group inhabits a virtual world within a computer network, others exist as robots, and still others have used genetic engineering to customize their form, giving rise to numerous humanoid species.
The story focuses on the digital world, exploring the challenges of life unending, and the pursuit of knowledge for its own sake. Then a tragedy injects fresh importance, forcing the characters to reevaluate their understanding of the universe.
In the face of this new threat they regroup, embarking on a journey to find other intelligent lifeforms, in the hope that they have answers. On their journey they encounter many strange lifeforms, each representing a unique way of living, but eventually they are confronted by a single truth that all species must face, if they survive long enough.
The story is rich with philosophical and scientific theories, including extra dimensions, the nature of existence, consciousness, and the purpose of life. The writing is very challenging, with numerous words invented to express the unique ideas of the story.