Sea of Poppies by Amitav Ghosh.
I'm reading this at the moment. It's the first part of a trilogy but the other 2 aren't out yet. I'm worried I'm going to finish and be frantic for the next one. It will be like Harry Potter - except instead of pining for witches, wizards and evil lords - I will be pining for Indian slave-traders, giants and mem-sahibs.