Absurd flowery prose, but this ancient bestseller was recommended to me because I too at one time wore a hat like that. It's the story of Iris Storm, who wears a green hat, drives a yellow Hispano-Suiza, and deliberately presents herself as a woman of easy virtue because she has a dark, dark secret in her past - the sort of secret that only a woman in a 1920s bestselling novel could have. It's all champagne and characters called "Boy" and "Venice" and glittering Mayfair nightclubs and people saying, "Darling, darling, DARLING!" to one another. Iris lives in Shepherd's Market and the novel's narrator, of course, is fascinated by her.
The author, Armenian-born Michael Arlen, once declared "Per ardua ad astrakhan" (he was wearing an astrakhan coat at the time) and for that I will always love him.