I regularly read what are known as "crime" novels, both in English and in French. It is interesting to note that these are known in French as "romans policiers", or "polars" for short. As if the police were the key element, and not the crime. In fact they usually are, since the crime has often been committed before the book starts, and anyway does not take up much space even if the act or acts are described in the book. Nevertheless, not all the heroes of such literature are actually members of a police force. We also have private eyes, professional or amateur, insurance inspectors, and even lawyers (Micky Haller in some of Michael Connelly's books, for instance). It would perhaps be truer to say that it is the solving of the unknown elements surrounding a crime, such as its motivations, circumstances, and main actors (ie the criminals) that lie at the centre of these books.
When a character in a crime book lasts over the space of several books, he (or she) becomes a sort of recurrent hero (or anti-hero), and the books become subtitled with his or her name, and can even take over, to some extent, from the writer's reputation. Kurt Wallander, Harry Bosch, Spenser, Sunny Randall, V.I. Warshawski, Pepe Carvalho, Rebus, Nick Stefanos, and others fall in this category; and you are probably beginning to get some idea of my reading habits by now!
The author may consider at some point that this has gone too far, or else become simply bored with his main character. He may also have a more multiple literary career to manage. He then has the problem of how to make his "hero" disappear, without necessarily losing potential readers for his other books. They may get killed in the course of action, so to speak. They may lose their central role, and just fade into the background, becoming occasional bit-players in later novels. This was the strategy used by George Pelecanos for his early main character, Nick Stefanos. Or the author may simply cease writng about them altogether.
One of the most original techniques that I have noticed being used is that adopted by Henning Mankell in his latest book starring his police detective, Kurt Wallander. The book is called, in English, "The Worried Man" or "the Troubled Man", it depends on the versions. Wallander has always been of the anti-hero ilk. Solitary, drinking too much, over-weight and chronically depressed a lot of the time, except when he is at work. Things get worse during this latest opus which almost certainly signs the end of Wallander, as we learn at the end, after several brief flashes when he forgets where he is, that he has Alzheimer's disease. There, I've done what one should never do when reviewing a "crime book" by telling the end of the story! But there is, as usual with Mankell's books that revolve around Wallander (he writes a lot of other things too), much more to the book than this, and I haven't even mentioned the plot. It is, amongst other things, a close look at some of the dark political past of Swedish society, and a very good "crime" novel. But I am sad to see Wallander go. Maybe there will be a cure for Alzheiner's disease in the future. What was the guy's first name again?
And here is a musical present: Worried Man Blues by the Abbot Family.
We don't know how Kurt Wallander sings. Probably not very well.