Invisible ink! How could she have missed it? By the moonlight, with her nightvision especially, it is more noticable, but only if you tilt the book just so...but Bronte, clever bookwyrm, must have noticed. Even with her gifted eyes, Zara must squint. But she can read whole new options at some of the chapter choices... and more tricky, the whole new options don't give the page number straight, but rather as math choices and equations.