How Ms. Lepucki ended up as perhaps the only author to benefit from the Amazon-Hachette spat over pricing is a tale of almost unbelievable luck. And it has a twist: Her husband, Patrick Brown, is employed, in a sense, by Amazon. He works for Goodreads, a social network and peer recommendation engine for books; Amazon acquired it last year.

“Amazon has historically been a bully, and I don’t shop there,” Ms. Lepucki said. “But I love Goodreads. For the record. And my marriage.”

Mr. Colbert’s promotion of “California” started with Sherman Alexie, an anti-Amazonian and National Book Award winner for “The Absolutely True Diary of a Part-Time Indian.” Mr. Colbert invited Mr. Alexie on his show and asked him to bring a book by an author penalized by Amazon’s refusal to take Hachette preorders. Mr. Alexie said that he asked Hachette for a few advance copies of books by debut authors to peruse.

“California” was on the top of the stack. “I honestly suspected it wasn’t going to be my kind of book — too earnest,” Mr. Alexie said in a telephone interview. “But I started reading it, and it turned out to be an earnest page turner.”

With its post-apocalyptic setting, “California” mines a very busy vein in contemporary fiction. But Ms. Lepucki sees it as a love story. A young couple, Frida and Cal, have fled the ruins of Los Angeles to make a home in the wilderness. Everything changes when Frida becomes pregnant, and they leave isolation for a strange settlement filled with threats.

It seems impossible that a story with such dark undercurrents could spring from someone so laid-back and gregarious. Over breakfast in Los Angeles, where she grew up, the freckled Ms. Lepucki displayed a surferish vibe, right down to the wet blond hair that she twisted to the side as she spoke. Still, her eyes, which are a striking shade of blue, had a tendency to flash mischievously.

Image Ms. Lepucki signed thousands of copies of "California." Credit... Leah Nash for The New York Times

“I have a darker imagination than most people,” she said. “If you don’t ponder the end of the world on a regular basis, I don’t think you’re really human.”