The Above-Average Adventures of Nicholas Herriman: The Losers League, Book 1 (Unabridged‪)‬

Nicholas Herriman stands a good chance of being voted "The Most Average Kid to Ever Attend Peabody School"...until he stumbles on a trunk full of clothing and accessories that give him superpowers. Unfortunately, he doesn't know how to use the things in the trunk, and some of them are broken. 

Can he figure out the secrets of the trunk before he gets himself killed or gets creamed by his nemesis Harley Davison? And who is the mysterious figure following Nick around?