Just finished reading this novel, which introduces quite a few new ideas, including "Quantum Fronts", and "Quantum Regions" within the universe, in which there are differing methods for spaceship propulsion, computers that can send problems back in time and more.

Once it got going, it was quite a fun read, but the first 60 pages were a bit tough as it established the background for the story. Luckily, it redeemed itself later on, and it all made sense.