The Lost Years of Merlin by T.A. Barron

Details:

Published in 1996 by Penguin.

I think I read it in 2001.

From the Publisher:

Washed up on the shores of ancient Wales, the boy had no home, no memory and no name... he was determined to find all three.

This best-selling Tseries follows the adventures and training of young Merlin on the mist-shrouded isle of Fincayra, an enchanted land between earth and sky that is being destroyed by blight. With this land's inhabitants to guide him, the boy will learn that Fincayra's fate and his own quest are strangely intertwined.

He is destined to become the greatest wizard of all time--known to all as Merlin.

First Line:

It was the hand of a boy.

Alternate Cover: