The Snow Spider (Magician Trilogy) by Jenny Nimmo
This is a wonderful trilogy. The books are short and quick, but the stories are action packed and the characters are engaging. Once you start reading the books, you can't put them down. My only complaint would be that there aren't enough books in the series. Snow Spider is probably my favorite book in the trilogy, because the main character Gwyn uses magic more than in the other books.
Description:Ever since Gwyn's sister Bethan disappeared five years earlier on his birthday, everyone ignored his the day. But on his 9th birthday Gwyn's mom threw him a party and his grandmother gave him five strange gifts, which she claimed would prove his magical talent. On Nain's instruction, Gwyn released the objects one by one into the wind in hopes of receiving his heart's greatest desire - the return of his sister. Can Gwyn's raw magic bring Bethan home, or will it bring more evil into the lives of his family?