Artemis Fowl and the Time Paradox. Eoin Colfer
Artemis Fowl is no stranger to trouble. In fact he's a magnet for it. Man-eating trolls, armed and dangerous (not to mention high-tech) fairies, flame-throwing goblins - he's seen the lot. He had decided to forego criminal activity of the more magical kind. However... Now his mother is gravely ill.