It recently struck me how hugely popular the fiction genre of "mystery" really is. (I take the term to include all the subtypes like police procedurals, etc. -- anything in which a crime, usually a murder, is being solved.)
Just yesterday in my morning paper, two different authors were mentioned, each of whom has written well over a dozen novels in the genre, and neither of whom I'd ever heard of (though I do read "mysteries" occasionally). And it's also very typical for the same paper's weekly reviews to include at least one new entrant in the genre.
Since I was in my community library anyway, I took occasion to look at the separate section they devote to the "mystery/detective" novels, and was amazed to see it rivals the space devoted to all other "general" fiction. The same, I know, was true in bookstores in the day when that antiquated style of merchandising emporium still existed. It hardly does any longer.
OK, so what's behind the inexhaustible demand? I enjoy a good mystery now and again. There's a certain entertaining challenge in reading one, because in print the author can always just hide or downplay key details to be brought to the fore when he/she wants. On the other hand, on film or television, the medium requires stories to be simplified, and extraneous details eradicated, so a weird detail stands out like a sore thumb just by virtue of being mentioned; besides, we always know "who dunnit" because certain actors always play the bad guy.
I suppose most of us enjoy the idea of a little suspense, a little matching wits with the writer. But I would also guess that another important reason there seem to be so many mystery writers, and so many mystery novels, is that the typical such novel can be read in just a few hours. Those who choose to fill their reading time with mysteries will need a lot of them.