See my response below regarding note cards. As an alternative, a twice-folded sheet of letter size paper may be more available and gives you much more space. I

See my response below regarding note cards. As an alternative, a twice-folded sheet of letter size paper may be more available and gives you much more space. I lay the card down either beside the page I am reading or on the back cover (you can affix with tape if this makes it easier) depending on the size of the book.