Ultragoth, by Marc Levinthal

When down-on-his-luck musician Darby Louvin is accidentally caught up in the slipstream of goth-loving, parallel-universe-shifting outlaw Harold Dalener, he's transported to an empty Los Angeles where a 1918 superflu has wiped out most of humanity: the home of the "Ultragoths." As an unknown entity begins to pick off the Ultragoths one by one, Harold and Darby must chase the killer across the dead continent to New Orleans, where the real gothic showdown begins. Fans of alternate history, zombies, giant robots and extra-dimensional baddies are in for a bumpy, exciting ride with Marc Levinthal's Ultragoth!