Here is Where I... Wield a Really Big Sword

Gideon Thump knows magic abounds in his town, that a tight crew of his classmates are secretly champions of the light and face down evil on a daily basis. All he needs is proof. He foolishly trails their leader and soon finds himself no longer a simple observer. Dropped inadvertently into the role of the major hero, with heavy sword and all, Gideon must win over a supporting cast that blames him for the loss of one of their own, while facing down magical baddies that are thoroughly modern and a little absurd.
Making matters worse, his annoying cousin moves in with him and runs afoul of magic herself. With a sinister foe dead set on harvesting Gideon's fledgling magic, he must rally the troops and employ his addled wits to carve out a destiny that doesn't result in him shuffling off this mortal coil.