novelization
From Longman Dictionary of Contemporary Englishnovelizationnov‧el‧i‧za‧tion (also novelisation British English) /ˌnɒvəlaɪˈzeɪʃən $ ˌnɑːvələ-/ noun [countable] the story that was told in a film or television series, written afterwards as a book the novelization of Terminator 2