Althugh Michael Bennett ended up being credited as the author of the book, even during the original run it was acknowledged by those involved that he was not the author.
At some point before the Broadway opening, Michael Stewart, the original book writer, asked that his name be taken off the book, presumably because he was unhappy with how many changes had been made to his work. Work had been done on the book by lyricist Dorothy Fields (who was also an experienced librettist). Neil Simon had also done work on the book. In a post-opening article in the New York Times, it was said that he only edited what was already there, but other sources have said that he supplied a good deal of new dialogue. But neither Fields nor Simon wanted credit, so Bennett agreed to be the credited author of the book.