I've been on a Dorothy Sayers read-a-thon. I started with "Strong Poison" in June (as per July 4th blog post). I finished "Have His Carcase" mid July. And then devoured "Gaudy Night". I just finished "Busman's Honeymoon" August 18th. Of the four, I think I enjoyed this last one the best of all...although I wouldn't have if I hadn't read the first three to understand the background of their relationship.
These four books are the main books that deal with the Lord Peter Wimsey and Harriet Vane's relationship. I loved the interactions between those two characters (and Bunter!)...with a few mysteries thrown in as well. There was quite a bit of French and Latin thrown in also. Most of that I had to let go over my head. I would have loved a translation of the French letters near the end though.
Sayers also started "Thrones, Dominations" but it was finished by another author....who also wrote another Peter/Harriet novel after that. I'm still deciding if I should continue on. There have been very mixed reviews about both of those novels. But I don't know how I can resist not reading them....even if the last reads more like FanFiction rather than something Sayers would have wrote. Not all FanFiction is horrible.
Here is a website with the chronological list of the Lord Peter Wimsey short stories and novels with some reviews and plot points.