The King's Buccaneer - Raymond E. Feist

Long recovered from the ravages of the Riftwar,
the land and people of the kingdom of the Isles
thrive. Nicholas, the youngest son of Prince Arutha,
is intelligent and gifted but vastly
inexperienced. In hopes of hardening him, his father sends him
and his irreverent squire, Harry, to live at
Rustic Castle Crydee to learn of life beyond the halls
of privilege. But within weeks of Nicholas and
Harry's arrival, Crydee is viciously attacked by
unknown assailants, resulting in murder, massive
destruction, and the abduction of two young noblewomen.
The raiders have come from a pirate haven and are
no ordinary foe ... but an enemy connected to dark
magical forces that threaten the lands Nicholas
will someday rule -- if he survives.