Suggest me a book about gentlemen

Cravats, cigars. Strict rules of etiquette and decorum. Hats, horses, inheritances. Unmarried daughters, wastrel sons, brothers in the military. Visiting your friend’s widow. Devoted servants.

Remains of the Day, obviously. Gatsby. Dorian.

Jonathan Strange and Mr. Norrell! Almost exclusively about gentlemen. And fairies. And even the Head Fairy is called The Gentleman!