There are many reasons we might pick up a detective novel. One is obvious and very simple:
We know we enjoyed the last one.
Maybe that — the fact that we are comfortable — means that detective novels will never be great art.
Simon Schama has said:
“Great art has dreadful manners … the greatest paintings grab you in a headlock, rough up your composure, and then proceed in short order to re-arrange your sense of reality.” from The Power of Art, 2006.
This goes for great literature too. Think of …. well, 1984, or The Narrow Road to the Deep North, or A Little Life … You’ll have your own examples that spring readily to mind. Great literature challenges us. It changes us. It is upsetting.
And look, great art and great literature are wonderful. We couldn’t live without them. Really.
It’s just that sometimes you don’t want to be shaken or enlightened or challenged. Sometimes you just want to curl up and have an easy time, with the thing you already know.

And murder mysteries are something we all know. The conventions surrounding them are well known by authors and they give their own kind of aesthetic pleasure. Michael Cohen says:
“Conventions themselves are pleasure-giving because they allow art in the first place and because they allow the audience to relax into relied-upon patterns of received stimuli.” Murder Most Fair, p26.
Dennis Porter (1981) believes that conventions promote ‘intelligibility’ and make novel reading easy.
Familiarity is reassuring. Psychological studies have found that familiar things are more likable, because they make us feel comfortable. If you like, you could imagine that this is a product of evolution. If something is familiar, that means we have been exposed to it before … and we are still alive. We are programmed to believe that familiar things are safe.
Whatever the reason lying behind it, a genre fiction reader will be able to tell you that, for them, part of their enjoyment of a new book will come from the fact that it is very similar to the last one.
Does that mean they cannot be taken seriously as literature?
References and further reading
Cohen, Michael (2000), Murder Most Fair: the Appeal of Mystery Fiction. London, Cranbury N.J.: Associated University Presses.
Friedman, Susan S. (1991), “Weavings: Intertextuality and the (Re)birth of the Author”. IN Clayton, J. and Rothstein, E. (eds), Influence and Intertextuality in Literary History. Madison, University of Wisconsin Press, 146-180.
Porter Dennis (1981), The pursuit of crime: art and ideology in detective fiction, Newhaven: Yale University Press.
Raghunathan, Raj (2012), “Familiarity Breeds Enjoyment”, Psychology Today, Jan 2012
Schama, Simon (2006), The Power of Art. New York: Ecco.
IMAGES
http://londonicon.co.uk/power-art/schama-power-art/
‘Jimmy Perez’s House’, Lerwick by Mike Pennington under Creative Commons licence.
“Black-capped Lory drinking nectar” by derivative work: Snowmanradio (talk) via Wikimedia Commons