Funny Girl by Nick Hornby

Several of Nick Hornby's books have been adapted into movies (High Fidelity, About a Boy, A Long Way Down, and Fever Pitch), and he's written a few screenplays himself. Funny Girl (no relation to the Streisand musical) is his first novel to not take place in the modern age, deals with the act of writing itself, and in my opinion would make a good film.

In the mid-1960s, Barbara Parker wins the beauty pageant in her hometown of Blackpool, England, but would rather be known for her sense of humor over her looks. She takes off for London with the goal of being a comedic actress like her idol, Lucille Ball. Her agent encourages her to change her name, and they settle on Sophie Straw. She soon gets an audition for an episode of BBC's Comedy Playhouse, which has long been a springboard for full-series orders of sitcoms.

When the writers of the episode, Tony and Bill, ask Sophie what she really thinks about their script Wedded Bliss?, she prompts them to throw the whole thing out, and on the spot they decide to write a new version based around her. Ironically, they decide the female character should now be named Barbara and hail from Blackpool. Then they change the name of the show to Barbara (and Jim), the parentheses (or "brackets" in Brit-speak) indicating the dominance of Sophie's character over her husband, which does not please her vain co-star, Clive.

Barbara (and Jim) becomes successful enough to run for four 16-episode series (seasons). The lives of the writers and stars are used for inspiration for the show's plots. Sophie and Clive begin a relationship and eventually become engaged. Tony is in an uncomfortable marriage until he has a baby with his wife around the same time that Barbara and Jim have one in the show. Co-writer Bill is a closeted homosexual who writes a novel based on his outsider status, and producer Dennis gets a divorce and realizes he's in love with Sophie. There is some intersection with real events, like when Lucille Ball is shooting Lucy in London, Sophie gets an underwhelming conversation with her idol.

The last couple chapters jump forward to present day, but I won't say any more since you should discover the circumstances for yourself. Funny Girl is a purely entertaining book that explores whether entertainment itself should have a deeper purpose, or if it's "enough" to be writing something that people enjoy.