There really is no such thing as too many books, right?
I tend to fill my books with stuff I pick up while I read them, too. Things like receipts, tickets, scraps of paper, notes and much more quite often end up in whichever book I am reading at that particular moment. They end up as little reminders of where I was or what I did when I read the books, like little surprises or treasures for the books to keep.
Anyone else doing the same?