These days shorter fiction is almost always published as part of a collection, unless you are selling on line or self publishing in print.

Is this in response to the wrong comment? I'm giving an example of the opposite of what you're saying.

What I meant was that books like the Maigret novels probably wouldn't be published as free standing books, but packed into collections, say three or four of them together, to get closer to the magic 500 pages.

I will mention that I highly recommend Simenon's writing, Maigret series and others. He's a fine writer. The TV series with Michael Jambon is excellent. The Maigret stories are the right length to turn into an hour show without losing too much of the interesting details.

You can literally buy these as paperback though, directly from the publisher: https://www.penguinrandomhouse.com/series/IMA/inspector-maig....

Of course, but remember that they were first published in 1931. The last ones were 1973 but by then they were so popular they could go against the already established trend of longer books.

Someone writing new mysteries today probably could not get a single book that short accepted by a publisher.