The only other one I've read is "Tragedy at Law" -- which works very well if you see it as a semi-satirical exploration of circuit court justice, but less so, if you're expecting it to be a traditional murder mystery, which it most certainly isn't; and not only because the death to be investigated occurs only in the last part of the book ... and is cleared up, by Inspector Mallett and Hare's other series detective -- a lawyer named Francis Pettigrew, who is introduced in this book -- acting independently, but coming to the same conclusion, very soon after the death has occurred. (There is another death earlier in the book, but the "who, how and why" of that first death is not a question -- though it IS part of the setup which triggers pretty much everything else in the novel.)

I think BT has read another one of Hare's nonseries books; maybe she'll share a bit on her experience with that one.

The Hare books currently still on my TBR (bought chiefly on the basis of what I could get my hands on at an affordable price) are:

Death Is No Sportsman (Inspector Mallett #2)
With a Bare Bodkin (Francis Pettigrew #2 / Inspector Mallett #5)
When the Wind Blows (Francis Pettigrew #3)
He Should Have Died Hereafter (Francis Pettigrew #5)
That Yew Tree's Shade (nonseries)

I read When the Wind Blows which deals with a death amongst an orchestra. I really enjoyed it, but mostly for the different characters interacting with each other and with Pettigrew - from what I remember about it. I also liked Pettigrew better than Mallet. I don't remember much about the investigation, it was the humor and the characters that made the book.

That's what more and more stands out to me as well -- humor, characters, and narrative tone; not necessarily plot. -- That said, based on your comments, I think I might enjoy "When the Wind Blows"; that's good to know!