I read all the Lord Peter Wimsey books in my early teens -- I have fond memories of borrowing Sevenoaks library's large-print editions, because the others were usually on loan, and reading them at arm's length. More recently I'd listened to some of the BBC radio adaptations of the books (which are mostly very good indeed), and I was surprised to discover that two more books had been written by Jill Paton Walsh in the late 90s.
This one's based on an outline and some fragments of a book that Sayers was planning to write but abandoned; it's set in 1936, some years after the last instalment of the story, and the authors therefore spend several chapters setting the scene before anybody dies. The mystery itself is standard Sayers fare, with an unusually dramatic (but reasonable) ending.
The obvious question here is how Walsh fares when writing a Sayers book. Well, I can't find anything to complain about; she nails Sayers' style very effectively, and develops the characters in an interesting and believable way. I'm now curious to read more of Walsh's work to see what her writing's like when she's not trying to imitate someone else; if it's half as good as this I'll be happy. Recommended.