Mine was an adult book by Dean Koontz called Sole Survivor, about a cop who lost his wife and daughter in an airliner crash with no survivors - until, impossibly, a woman shows up claiming to have survived the crash. I don't remember all the details, just that I couldn't put it down. Maybe it's worth a re-read, hmm?
I enjoyed your insights on The Giver so much, I'd love to hear from you again. Can't wait to be "creeped out".