Elfhome

#3 in the groundbreaking, award-winning Elfhome series. Pittsburgh, PA has been magically transported to a world of elves and magic in order to stave off a monstrous invasion of Earth.  Now Tinker must root out and destroy an evil plot.

Elfhome. A world of powerful magic, beautiful elves, man-eating trees, frost-breathing wargs, and god-like dragons. Pittsburgh. A city that has been stranded deep in virgin elfin forest to stave off an invasion by the merciless oni. Its population of sixty thousand humans and a handful of elves are pitted in war that will only end in genocide. Winter is coming. Supplies are running low. All political ties are fraying. Hidden somewhere in Pittsburgh's crumbling neighborhoods, a vanguard of oni are growing in number and attacking from the shadows. 
     Girl genius Tinker was once a human orphan, growing up on the Pittsburgh streets. Now she's an elf princess with all the bells and whistles. She rules over a melting pot of humans, elves, half-oni, and the crow-like tengu. Tinker is determined to make her city a place of freedom. She's going to have to kick butt and take names. Seven elf children are already missing -- and the oni eat their prisoners when they outlive their usefulness.