Few American writers sell as many books, live better or worry more than Dean Koontz.

“There are days that you think, ‘I can’t do this anymore,'” says Koontz, 77, author of more than 110 books that have sold over 500 million copies in 38 languages. “Of all the writers I’ve ever known, I have more self-doubt. I’m eaten by it all the time.”

Fears? He has a few.

Koontz writes terrifying stories of murder and mayhem, yet is incapable of watching a gory movie. He hasn’t flown for 50 years after a flight he was on encountered serious turbulence and a nun on board proclaimed, “We’re all going to die.” He’s not big on boats, either, after an anniversary cruise coincided with a hurricane. Mostly, Koontz stays put in Orange County. Easier, safer…