I'm the author of the ASHFALL three-and-a-half-ology: ASHFALL, ASHEN WINTER, SUNRISE, and DARLA'S STORY.
Really enjoyed this book. Fresh concept, very exciting, and a healthy dose of humor, too. The premise--two alien factions battling for control of Earth's future--would make an excellent video game. I'd envision something along the lines of X-Com or Jagged Alliance.