Knight Moves - Walter Jon Williams
This is a decent slice of '80s SF, picked up for a pound at the second-hand bookshop. It's the 28th Century and Doran Falkner is the richest and most powerful man in human space. In his student days, centuries earlier, he had a chance encounter with a powerful alien being and agreed to sell off Earth in exchange for the secrets of unlimited free energy and eternal life. Now humanity is scattered across the galaxy and Earth is depopulated; the huge galactic distances have caused civilisation to atrophy, and unless something can be done, the human race is in danger of fizzling out. With the discovery of some creatures on a distant world that seemingly have the power to teleport, Doran heads off with his team discover the science that may save humanity...
Yes, it's pretty formulaic, but it's very well written. The melancholy atmosphere of Earth's twilight years is similar to George R R Martin's Dying of the Light, and the relationships between the characters are intelligently portrayed. This actually reads like a much more mature book than Williams's recent Dread Empire's Fall series, despite the pedestrian plot and a few cheesy moments. It's not really original enough to recommend tracking down, but it's worth a read if you come across a copy.