The Number of the Beast
Robert A. Heinlein
 The book is a series of diary entries by each of the four main characters: Zebadiah John Carter, programmer Dejah Thoris "Deety" Burroughs Carter, her mathematics professor father Jacob Burroughs, and an off-campus socialite Hilda Corners. The names "Dejah Thoris", "Burroughs", and "Carter" are overt references to John Carter and Dejah Thoris, the main protagonists of the Barsoom (Mars) novels of Edgar Rice Burroughs. The four travel in Zebadiah's spaceship Gay Deceiver, which is equipped with the professor's "continua" device and armed by the Australian Defence Force. The continua device was built by Professor Burroughs while he was formulating his theories on n-dimensional non-euclidean geometry. The geometry of the novel's universe contains six dimensions; the three spatial dimensions known to the real world, and three time dimensions - t, the real world's temporal dimension, τ (tau), and т (teh). The continua device can travel on all six axes. The continua device allows travel into various fictional universes, such as the Land of Oz, as well as through time. An attempt to visit Barsoom takes them to an apparently different version of Mars seemingly under the colonial rule of the British Empire; but near the end of the novel, Heinlein's recurring character Lazarus Long hints that they had traveled to Barsoom, and that its "colonial" status was an illusion imposed on them by the telepathically adept Barsoomians: In the novel, the Biblical number of the beast turns out to be, not 666, but (6^6)^6, or 10,314,424,798,490,535,546,171,949,056, which is the number of parallel universes accessible through the continua device.