Book trilogy about apprentice boy using rune magic

Question

I've read a book trilogy some years ago. It was about a teen boy who was living with his mother on an island that nobody knows about. He shows extraordinary talent for rune magic and he gets a teacher to help him develop his talents. There was a magic gate that transports them to the another world. Then the series is set in the modern world. Rune magic is aligned with the stars and is not working in the modern world because of improper rune alignment with our stars.

Answer 1

Quadehar The Sorcerer by Erik L'Homme

The first book in this adventure saga introduces us to Robin, a boy who lives on the Lost Isle, a fantastical realm between the Real World and the Uncertain World where evil resides. One night, Robin's potential for magic is revealed in the presence of Quadehar the Sorcerer. Robin becomes the sorcerer's apprenctice and studies the magical secrets of the craft. His talents are put to the test when he and his friends must cross into the Uncertain World to save a classmate who's been kidnapped by monsters. Will Robin's newfound knowledge help them prevail?