[jcn363]

I must say I'm pleasantly and gratefully surprised with this (for me) unknown author.
The touch of humour (in almost all over the book) and the descriptions (I particularly enjoyed the inquest) have caught me.
The character seems a rare kind of human (perhaps due to the WWI). And indeed, he may finds out a way to be gay or to get married, but it's only the start of the series, the presentation of a character in progress in a real first book.
Well, Peter is not Sherlock or Hercule.
By Jove! Dorothy is not Agatha, but I think she could be a must in the detective story.
You can say it is the criticism of a detective story through a detective story. But please, remember: the key is the case and not the characters, and the characters speak by themselves. I mean the author lives his/her life and his/her characters live into a few letters. Just imagination. No more, nor less.
P.D.: I recommend her essay The Lost Tools of Learning.
In this essay, she suggests that we teach everything but how to learn, and proposes that we should adopt a kind of the medieval scholastic curriculum for methodological reasons.

Spoiler:

"What use is it to pile task on task and prolong the days of labor, if at the close the chief object is left unattained? It is not the fault of the teachers—they work only too hard already. The combined folly of a civilization that has forgotten its own roots is forcing them to shore up the tottering weight of an educational structure that is built upon sand. They are doing for their pupils the work which the pupils themselves ought to do. For the sole true end of education is simply this: to teach men how to learn for themselves; and whatever instruction fails to do this is effort spent in vain."

The changing world of last 70 years remains unmoved.

Good luck.