The Superhero's End by Lucas Flint

Banished to an alternate universe where superhumans have been hunted to exinction and the rest of the human race has been enslaved, Kevin Jason (Bolt) must figure out a way to return to his own universe in time to stop a supervillain who seeks nothing more than the destruction of Earth.

To do that, Kevin must break into a heavily-protected castle to gain access to the technology that can take him home, a task difficult even for a superhero with his powers.

Yet even if Kevin manages to return home, he may find himself walking directly into his enemy's trap.