The latest DC comic featuring the caped crusader is "an explosion from my gut reaction of what's happening now" and "a reminder to people who seem to have forgotten who we're up against," Miller said during a San Francisco comic book convention.
The story has Batman settling the score after terrorists attack Gotham City.
"It just seems silly to chase around the Riddler when you've got al-Qaida out there," he said. "Superman punched out Hitler. So did Captain America. That's one of the things they're there for."
A DC Comics spokesman declined to comment on the project, the New York Post said Tuesday, and an industry source added the book probably will not be published this year.
In addition to working on the 200-page novel, Miller is penning monthly Batman comics and three of his projects including a sequel to "Sin City," are being made into films.