Game books are books that, in addition to being read, are played like a game. Game books can include activity books, books with branching plot lines, hidden picture books, mystery books, and various other genres. Most game books are designed to be solitary endeavors for a single reader. Game books date back to the 1930s and peaked in America in the early 1980s, however, they were mostly killed off by the growing video game market. However, even to this day, they are still being made. I really liked game books as a child, and, to some extent, I still do.
These include books with assorted games and activities in them like crossword puzzles, word finds, cryptograms, coloring pictures, cutouts, and more. I loved these in elementary school.
Branching Plot Books
Branching plot books are stories where the reader is allowed to choose, from a limited number of options, how the plot will progress. Books like this include Choose Your Own Adventure, Lone Wolf, Find Your Fate, and many others. I owned about a dozen of these growing up and read more from my school's library. I preferred those with coherent stories rather than those that had dozens of completely unrelated endings.
Hidden Picture Books
These are books with collections of drawings in which pictures are hidden in them. Popular titles include Where's Waldo, For Eagle Eyes Only, and compilations of the Hidden Pictures from Highlights magazine. I still enjoy these today.