Here's a tip - use scrap paper as bookmarks. I go the extra mile sometimes and use items, like other books or pens or even phones. But anyways, scrap paper doesn't take up extra room.
I got these bookmarks once that said "get your green on." I found it a bit hypocritical, be green by picking up this little piece of paper you don't need. But alas, I did anyways. They have come in very handy as I read my multiple green books.