Axelrod did a pretty good job turning Capote's novella into a romantic-comedy. I think it was a clever idea to make the male author into a kept man - it gave his character a bit of meat, plus added an interesting character in the woman, and introduced Holly's ex husband in an interesting way.
This is really a showcase for Holly though - who is well captured. There are some lively support characters like Holly's friends, and hill billy husband. Axelrod's day of adventure works well and the Tiffany's scene - all his own work - a delight.
Interestingly the party scene in the script only goes for a short time - Blake Edwards expanded it on screen. Also the final speech in the cab from Paul isn't here - I think it was a good addition because reading this the ending felt a little abrupt.