A flip book is a book with a series of pictures varying gradually from one page to the next, so that when the pages are turned rapidly, the pictures appear to animate, simulating motion or some other change. Flip books are often illustrated books for children, but may also be geared towards adults and employ a series of photographs rather than drawings. Flip books are not always separate books, but may appear as an added feature in ordinary books or magazines, often in the page corners.
Flip books are essentially a primitive form of animation. Like motion pictures, they rely on persistence of vision to create the illusion that continuous motion is being seen rather than a series of discontinuous images being exchanged in succession. Because of this, flip book images will only appear on one side of the book's pages, so that rather than "reading" left to right, a viewer simply stares at the same location of the pictures in the flip book as the pages turn. The book must also be flipped with enough speed for the illusion to work, so the standard way to "read" a flip book is to hold the book with one hand and flip through its pages with the thumb of the other hand.
The first flip book appeared in 1868, and was originally known as a kineograph (basically, "moving picture"). They were the first form of animation to employ a linear sequence of images rather than circular (as in the older phenakistoscope). In 1895, Thomas Edison invented a mechanized form called the mutoscope, which mounted the pages on a central rotating cylinder rather than binding them in a book. The mutoscope remained a popular attraction through the mid-20th century, appearing as coin-operated machines in arcades and amusement parks.
Flip books have typically been viewed as a toy or novelty for children, and have been a common "prize" in cereal and Cracker Jack boxes. However, since their creation they have also been an effective promotional tool on such decidedly adult products as automobiles and cigarettes, and continue to be used in marketing of all kinds, as well as in art and published photographic collections. Vintage flip books are popular among collectors, and especially rare ones from the late 19th to early 20th century have been known to fetch thousands of dollars in sales and auctions.