Was this originally meant to be a novel? (theory)

The film's structure, very chapter like, emphasis on what are meant to be introspective moments for the characters, and slow burn pacing make me wonder if Ishiguro, someone who is mainly a novelist rather than a screenwriter, originally intended for WC to be a novel but for whatever reason turned it into a screenplay.

Anybody else ever get a 'novelistic' quality about WC?