The Dispossessed, by Ursula Le Guin

The Dispossessed, one of Le Guin's greatest novels, is the story of a brilliant temporal physicist called 'Shevek' (gotta love that name!). He is on the verge of discovering 'the Principle of Simultaneity', which will revolutionise galactic communications. Shevek's story is played out against two contrasting worlds: a struggling, resource-poor world called 'Anarres' that has achieved a form of the old anarchism, and its sister world, 'Urras', a rich and festering world not unlike Old Earth. Shevek is from Anarres, but in order to fulfill his life's work he must go to Urras, where he finds suspicion, treachery, incredible beauty and luxury, and the seeds of a new revolution...