The fifth book in the Artemis Fowl series.
 
TEENAGE GENIUS ARTEMIS FOWL HAS SOMETHING NEW TO PLAY WITH... DEMONS. Big human haters, they are (thankfully) stuck in Limbo, a place that exists outside of time and space. But now demons are materialising on Earth at random.

This won't be pretty... Artemis is determined to save the day (I know, everyone's shocked). Can he somehow help the demons, and avert the carnage and chaos of a human-demon war?He's not the only one on their trail, though. Meet Minerva Paradizo - ruthless child genius, and not quite so demon-friendly.

Let battle commence.