The pre-wave was Edgar Allan Poe, who was renowned on both sides of the Atlantic, and naturally, Arthur Conan Doyle. The first wave included Agatha Christie, Dorothy Sayers, G.K. Chesterton and others. The second wave included Josephine Tey and Ngaoi Marsh. Collectively, they explain delightful graphs like this one here.
Georgette Heyer's detective novels are quite good. Her romances are her strength. As I've mentioned elsewhere, one of the worries for me when it comes to writing historical fiction is getting minor details wrong. There's a delightful scene in Christopher Reeves Somewhere in Time where he shows up in the past wearing a suit that is about thirty years out of date--"Oh, look at you, wearing your grandfather's suit!" a lady proclaims--and this despite the character meticulously researching the time period beforehand.
Heyer didn't make those kinds of mistakes. She was the kind of researcher who did know the difference in fashion by thirty years.
Heyer would never stick a microwave in a 1950s novel.
As with Agatha Christie, I will be addressing tropes from Heyer. She used them! I'm a fan! She had the sweet-natured hero, the rake hero, the competent hero, the dopey hero, the mystery-solving hero. And she had heroines of all types as well, from the practical to the flighty.
Like Christie, Heyer could be amusing. The first book I ever read by Heyer, recommended to me by a cousin, was These Old Shades and a large portion of the book is taken up with the amusing antics--and dialog--of the rake hero's brother. The hero himself is deadpan saracstic.
Even more importantly, however, Heyer's
amusement never compromises her main characters. There is nothing more
disappointing than reading a romance whose author doesn't care for the
genre and thinks her romantic characters are kind of dumb and pointless.
Heyer cares that her characters get together. And so do her readers.