You could try searching for "Post-it Flags, 200/High Volume Desk Grip Dispenser" * They remove cleanly, if you're worried about permanently marking up or defac

You could try searching for "Post-it Flags, 200/High Volume Desk Grip Dispenser" * They remove cleanly, if you're worried about permanently marking up or defacing a book. * They are easy to write on (I've mostly used EF nib fountain pens). * Best of all, since they are color-coded, you can invent your own scheme (e.g. blue == "I should revisit this", yellow == "my top N favorite quotes from this book", etc.) Edit: to add another point * They are large enough that you can write a decent sentence in there -- the "page flag" size might be a tad too small for that (but thanks to the EF nib, I often find myself using different-colored flags).