It isnt in particular a 'girly' book but it greatly appealed to me. As Ellen Lee said, its a young Adult book, it doesnt aim towards either gender. The main protagonist is a boy, but it doesnt make it any less appealing.
Seriously, I highly reccomend it. Perhaps go to your local library and see if they have it, read the first few chapters, then decide to read on.
At first I wasn't too sure about it, then I got sucked in and couldn't stop reading.