State of Change is an original novel written by Christopher Bulis and based on the long-running British science fiction television series Doctor Who. The novel features the Sixth Doctor and Peri, although the dimensional instability of the realm they are currently visiting causes the Doctor to briefly regress through his first five incarnations; the Sixth Doctor also spends a great deal of time allowing the personality of the Third Doctor to take control of his body when he is forced to fight. Source: Wikipedia (en)