Copper

At first glance this looks like a book for kids, but it's not really. Granted, I can see a child reading this and taking superficial pleasure from the episodic adventures of a boy and his dog - it brings to mind Calvin & Hobbes - however, like (to a lesser extent) Calvin & Hobbes, there is a sub-text that you probably need a more mature outlook to appreciate. The main themes are about treating life as a adventure; taking the path less travelled; not being blinkered to the possibilities around you.

It makes me curious about the Amulet series, by the same author, which I believed is aimed at a younger audience but now I wonder if there is a similar additional subtext.