i've just started reading this excellent book and only tonight discovered that my sister is reading the same book to her 5yo and 7yo boys.

The imagery is amazing, the violence is minimal to nonexistent for a fantasy... just an amazing read and impossible to put down

Just like Harry potter, it can be found in the children's section (it is amazing how i've spent my life reading all the literary classics and now love the finds in the kids section that are just as wonderful for adults)

It is the bartimaeus Trilogy by jonathon stroud