Artemis Fowl and the Time Paradox by Eoin Colfer
Teenage criminal mastermind Artemis Fowl has a new mission - and this time it's personal. Artemis's mother is dangerously ill, and the only way to find a cure is for Artemis - with Holly Short by his side - to go back in time to battle his younger, more evil self . . .
Action packed and full of humour - a must-read for boys and girls aged 10+.