The Acolytes of Crane (Theodore Crane, #1)

Theodore Crane finds solace in goofy everyday pranks, in order to cope with living under the shadow of an abusive father and dealing with a belligerent bully who seeks him out at school.
One day, intervention from outer space strikes as a mysterious amulet soars into his room bearing enigmatic clues.
This causes Theodore to question everything about the universe, and the answer comes in the form of two battling intergalactic warlords who, unknown to Theodore, have been analyzing him all his life, fearing that he can unlock the secret to their defeat and demise. But this curiosity over Theodore comes at a price, for many people.
To protect his loved ones, and to avenge what has torn his family apart, Theodore must leave Earth. He is given just fourteen days to assemble a team of trustworthy friends and then convince each one to go with him on this dangerous mission.
The Acolytes of Crane is two parts; a coming-of-age story that delights us when it turns into a blast 'em, rock 'em space odyssey. In the words of one reviewer, it's "something like Sandlot to more like Ender's Game."