Have you ever bought a book, started reading it and then realised you have already read it? If so, how far did you get?
Now this hasn't actually happened to me, I normally remember if I've read a book or not, some time I can even still tell you about it for ages afterwards. However I did start reading Fallen again and even though I knew what was coming and when I even roughly remembered how much of the book I'd read previously I re read everything. I still didn't like the book but I'm in the process of writing a blog post about it so don't want to comment to much on here.
As I read more books I do see myself doing this more and more.