Eoin Colfer's Artemis Fowl books really defy an adequate description. To say they're about fairies, dwarves, elves, trolls and other 'fictitious' creatures just does them no justice at all.
These are definitely NOT the creatures from the old fashioned fairy fantasy lands of yore but are the high tech creatures whose technical abilities make mankind look pretty lame by comparison.
As for who exactly Artemis Fowl is then I'd simply say either by the DS 'game' (although calling it a game is not doing it justice) or buy the first book "Artemis Fowl" as a starting point and go from there.
The conceptualisation the characters and the plot lines are way and above that of many more respected works of a more adult genre.
Young children wouldn't like these stories, at least I dubt that they would but young adults should find them far more engrossing.
Far older adults will also, I'm sure find the stories absorbing and, in this format, are a good reason alone to treat yourself to a DSi