Incandescence — Greg Egan

The long-awaited new novel from Greg Egan! Hugo Award-winning author Egan returns to the field with Incandescence, a new novel of hard SF.
The Amalgam spans nearly the entire galaxy, and is composed of innumerable beings from a wild variety of races, some human or near it, some entirely other. The one place that they cannot go is the bulge, the bright, hot center of the galaxy. There dwell the Aloof, who for millions of years have deflected any and all attempts to communicate with or visit them. So when Rakesh is offered an opportunity to travel within their sphere, in search of a lost race, he cannot turn it down.
Roi is a member of that lost race, which is not only lost to the Amalgam, but lost to itself. In their world, there is but toil, and history and science are luxuries that they can ill afford.
Rakesh's journey will take him across millennia and light years. Roi's will take her across vistas of learning and discovery just as vast.