Day 2: A book you've read more than 3 times.
If I count the books of my childhood so many qualify. I'm picking Crusade in Jeans (Kruistocht in Spijkerbroek) because I've truly lost count of how often I have read it and the book on my shelf shows it. ALSO, THE TRANSLATION INTO ENGLISH SUCKS SO BAD IT MAKES ME WANT TO KILL PEOPLE EVERY TIME I THINK ABOUT IT. (See my review, which I will reblog after this).