Right now: The Hidden Reality
by Brian Greene.
Really, really good book. A must read for cosmologists, popular science fans or generally any science enthusiast. Right on scale with Greene's previous works.
Also, I'm about to begin with En Gammel Romfarers berettninger
(in English: "The accounts of an old astronaut") by Jon Bing. Norwegian science fiction that has never been translated to English as far as I know. I read it once before a decade ago; it's about an old astronaut who describes his journey to various stars and planets around the galaxy, and his encounters with the societies that live on them.