I'm the author of the ASHFALL three-and-a-half-ology: ASHFALL, ASHEN WINTER, SUNRISE, and DARLA'S STORY.
I really like the Tom Cruise movie based on this book, so of course I had to read it. It's better. The science fictional elements make a lot more sense, and Sakurazaka doesn't settle for a cloying and cliched Hollywood ending. If you enjoy fast paced, dark sci-fi, you'll love this book.