A very good fantasy novel. In fact this might be hard fantasy, in that there are some (admittedly fairly weird) physics behind the fantasy world, and not really any magic.
It's set in the future, and the main character is a starship pilot. He lost his ship, and later turned up somewhere far removed claiming he and his wife and daughter had been in another world. Once further evidence of this world appears, his old employers get him to go back and explore for them.
The world was fascinating, and I really enjoyed finding out all the little bits about it as the book went on, despite generally being bored to tears by fantasy novelists showing off their world. I think the main difference here is that the world is actually quite original and interesting (with not an elf, dwarf or wizard to be see).
On top of that, the main characters are all interesting. In particular, Quinn the pilot, who is perhaps the most bitter person imaginable after all that has happened to him, and who agrees to the company's mission as a way to get back and find his family.
Good stuff, I look forward to the second one in the series