I am currently reading a series called Gregor the Overlander. I think it is really cool. I don't want to spoil it for you, but it centers around an under ground world that was inhabited in the 1600's. Due to space and an abundant food supply, the animals down there have grown to a large size. The humans down there have many prophecies, and Gregor is centered in almost all off them. I really like the series, and I think that you would like it too. Here is a picture of the series.
The series in story order.