Artemis Fowl series

When a twelve-year-old evil genius tries to restore his family fortune by capturing a fairy and demanding a ransom in gold, the fairies fight back with magic, technology, and a particularly nasty troll.

Criminal mastermind Artemis Fowl is back and so is his brilliant and dangerous enemy, Opal Koboi. At the start of the story, Artemis has no memory of the fairy people and has returned to his unlawful ways. In Berlin, he is preparing to steal a famous Impressionist painting from a German bank. He doesn't know that his old rival, Opal, has escaped from prison by cloning herself. She's left her double behind in jail and, now free, is exacting her revenge...

Artemis's mother has contracted a deadly disease -- and the only cure lies in the brain fluid of African lemurs. Unfortunately, Artemis himself was responsible for making the lemurs extinct five years ago. Now he must enlist the aid of his fairy friends to travel back in time and save them. Not only that, but he must face his deadliest foe yet...his younger self.

Seemingly nothing in this world daunts the young criminal mastermind Artemis Fowl. In the fairy world, however, there is a small thing that has gotten under his skin on more than one occasion: Opal Koboi. In The Last Guardian, the evil pixie is wreaking havoc yet again. This time his arch rival has reanimated dead fairy warriors who were buried in the grounds of Fowl Manor. Their spirits have possessed Artemis's little brothers, making his siblings...