Gamebooks are generally linear, meaning the reader cannot circle back to an earlier passage, which means the narrative forms what graph theory considers a directed rooted tree. There are many exceptions, like when a gamebook brings you to a dead-end and requires you to go back to the entrance. Gamebooks are typically written in the second person with the reader assuming the role of a character to experience the world from that character's point of view (e.g. 'you walk into the cold and dark forest'). Many gamebooks form series with a common theme, trade dress, and/or ruleset. While each book is typically a stand-alone narrative, there are gamebook series such as Steve Jackson's Sorcery! that continue the narrative from the previous books in the series. History Origins There are several examples of early works of art with branching narratives. The romantic novel Consider the Consequences! by Doris Webster and Mary Alden Hopkins was published in the United States in 1930, and boasts "a dozen or more" different endings depending on the "taste of the individual reader". The 1936 play Night of January 16th by Ayn Rand, about a trial, is unusual in that members of the audience are chosen to play the jury and deliver a verdict, which then influences the play's ending: guilty or not guilty. Also quite early on, the possibility of having stories branching out into several different paths was suggested by Jorge Luis Borges in his short story "An Examination of the Work of Herbert Quain" (1941). This story features an author whose novel is a three-part story containing two branch points, and with nine possible endings. Another story by Borges, titled "The Garden of Forking Paths" (1941), also describes a book with a maze-like narrative, which may have inspired the gamebook form. The children's book Treasure Hunt, published in 1945 in Britain under the name of "Alan George" (probably a pseudonym), is another early example of a story with multiple paths for the reader to follow. Programmed learning materials, first proposed by B.F. Skinner, have been recognized as an early influence on the development of branching path books. This learning method was first applied in the TutorText series of interactive textbooks, published from the late 1950s up until the early 1970s. These books present the reader with a series of problems related to a particular area of study, allowing him or her to choose among