From the manufacturer:
On the Go Game Books make the perfect travel toys! Each of these fun-packed activity books for kids includes an invisible-ink marker that stores right in the front cover. Pop it out to color in scenes, complete crosswords, follow mazes, find hidden pictures and more . . . and see Surprize Ink images appear as you color! Includes 24 animal-themed pages, bound in a compact tablet format with a rigid back cover to support comfortable laptop coloring.