Dragon Orb (Dragons of Daegonlot, Book One

Daegonlot: a floating island separated from the mainland of Darkenfel, and home to the last of the dragonriders. At 16 years old, Daxon knew he was too old to be chosen to be a dragonrider. On his way home one night he was surprised when a wild dragon's egg was left in his care by the largest dragon he had ever seen. After the egg hatches, Dax is forced to flee from Daegonlot to protect the young dragon, and thus starts a journey to right an ancient wrong.