Ex-Heroes By Peter Clines

The first in a spectacularly genre-mashing adventure series that pits a small group of courageous, flawed, terrified superheroes against hordes of undead.

Stealth. Gorgon. Regenerator. Cerberus. Zzzap. The Mighty Dragon. They were heroes, using their superhuman abilities to make Los Angeles a better place.

Then the plague of living death spread around the globe. Now, a year later, the heroes struggle to overcome their differences and recover from their own scars as they protect the thousands of survivors huddled in their film-studio-turned-fortress, the Mount.

But the hungry ex-humans are not the only threat the survivors face. Across the city, another group has grown and gained power.
 
- Goodreads Summary