Because they are about Godless people.
All deep writing about the Godless is glum.
There’s no rational reason to be happy unless one believes in G-d and participates in an organized religion.
Look at me. My writing overflows with joy because I’m God’s humble servant. My every action is governed by His immutable moral law.
Joe Queenan writes in today’s L.A. Times:
Take the Scandinavian Whodunit Boom. A month ago, Karin Fossum’s novel, "The Indian Bride," won the Los Angeles Times Book Prize for best mystery. Fossum, a glum Norwegian, beat out a moody Swede and a German who writes about a severe Finnish cop. It’s Swedish." And a first-class mystery it was, the latest in a series by Swedish novelist Henning Mankell featuring the chronically depressed detective Kurt Wallander. (Some may argue for Agatha Christie’s Hercule Poirot or Miss Marple, but Christie is a conventional mystery writer whose work never even vaguely approaches the level of art.) Then I began gobbling up Mankell’s numerous proteges and imitators.
Finally, I began giving Swedish murder mysteries to fellow mystery lovers as anomalous Christmas presents. Wallander did not wear cool clothes and did not have a cool record collection and did not have any cool friends and was not an oenophile.
Mystery lovers are a finicky breed; we share a love of the genre but do not love all its practitioners equally. My sister Agnes has read all of Christie, who leaves me cold, while I have devoured 100 books by Simenon, whose charms remain elusive to most Americans. The only other hard-core Maigret fan I know is an ex-Marine who flies corporate jets, does not speak French and has no use for most other mystery writers.
My sister Eileen passes along every Ruth Rendell mystery she reads, while I send her the latest book by Fred Vargas, the pseudonym of a French medievalist whose 12 mysteries center on a weird cop named Jean-Baptiste Adamsberg. A friend of mine, 32, in a spectacular deviation from officially sanctioned generational behavior, was very involved in the punk rock movement of the 1990s, yet has read all 72 of Rex Stout’s Nero Wolfe books.
Mysteries set in foreign climes have steadily grown in popularity in recent years.
Since I got started on my Scandinavian mystery jag, I have read the Inspector Van Veeteren novels by Hakan Nesser, the Inspector Lindell series by Kjell Eriksson, the Inspector Winter novels by Ake Edwardson and two Inspector Huss novels by Helene Tursten. Every one of these writers is good, but in my book, Arnaldur Indridason is even better.