 Forward was the scientist and Larry Niven the author in a tutorial on science fiction writing , and later that evening Forward and Niven agreed to collaborate on a novel on aliens on a neutron star . However , Niven soon found himself too busy with Lucifer 's Hammer , on which he was already co @-@ writing with Jerry Pournelle . Forward wrote the first draft himself , but several publishers suggested the story should be rewritten by Niven or Pournelle – who were still busy . Finally editor Lester del Rey provided comments that guided Forward through two rewrites , and del Rey then bought the novel . Forward described the work as " a textbook on neutron star physics disguised as a novel " . 
