Margery Allingham was the best golden age crime author and Campion is the best detective. his business card said it all:
Coups neatly executed
Nothing sordid, vulgar or plebian
Deserving cases preferred
Police no object
Here are thirteen of her books in a Penguin classic crime edition from (I'm guessing) the 80s or 90s. These are nice and clean and shiny. You can't buy them separately, but why would you?