It is based on John Van Druten 's 1951 play `` I Am a Camera '' , which was adapted from the short novel `` Goodbye to Berlin '' ( 1939 ) by Christopher Isherwood .
The musical was based on the 1939 novel , `` Goodbye to Berlin '' by Christopher Isherwood , and the 1951 play , `` I Am a Camera '' by John Van Druten .