Have you ever bought a book, started reading it and then realised you have already read it? If so, how far did you get?
Not bought, but rented. When I did The Lord of the Rings readalong in 2010, I was under the distinct impression that I had started the novel in fifth or sixth grade (around the time the movies came out), but had never finished it. To my memory, I had ditched it after the Council of Elrond. As I reread it, though, things were so familiar—and not because of the films—that I realized I must have finished or at least skimmed the novel in that juvenile attempt. It was an odd feeling to be sure. Naturally, I finished the novel; it’s The Lord of the Rings. I’ll never not finish that!