Shopgirl - Reaction

Okay. About a Vermont girl looking for love in Los Angeles. Written by, starring, and directed by Steve Martin. Has a reasonable idea at the core but the execution is poor. e.g., an omniscient narrator that only appears three times. And is the narrator meant for comedy? For exposition on topics the actors aren't good enough to portray? An excuse to get text from the book directly into the movie? Also, the psychological change that the characters undergo is under-expressed. It's too important to be given as short shrift as it is.