Kurt Wallander is a grim man. Whether you meet him in books, or in the TV series, you will seldom see him (or read about him) smile. Both Branagh & Henriksson, who have played him in the English & the Swedish series, know this well. In fact, Branagh has even admitted to visiting flower shows to cheer himself up from the starkness of his screen life.
The hero of Henning Mankell's several mystery novels is a police inspector in the Swedish town of Ystad. He is a fictional detective, yes, but if you are thinking of the cocky Sherlock Holmes, then you are way off. For starters, Wallander doesn't jump from windows like Sherlock (as Mr. Downing or Cumberbatch have lead us to believe). If you are now thinking of the smiling, more laid back Poirot, then cut the mustache, the smile and add a lot of severity and self-doubt instead.
I have only read two Wallander books, so my impression of him is largely from what I have seen on the tv series. I have come to like this detective who has doubts, who is not perfect, who is stubborn, and labors through investigation (instead of having some elementary interventions). He is a very good police officer, but he gets into each difficult case with a reluctance, as if dragging himself to the gym, hoping he will find it closed when he reaches there. But once he is there, he goes all in, forgetting everything else - sleep, personal commitments, food.
Wallander brings detection face to face with existentialism. He is confused with the world around him, always trying to make sense of himself, and struggling to be a good policeman in the ever-changing Sweden. Having failed as a husband,, he is also constantly worried about being a good father, which is difficult with a rebellious daughter like Linda. He is anxious that he forgets to keep appointments with his father and does not spend enough time with him. In essence, Wallander brings to front all the angst of the modern man - is he doing enough? Is he capable? What should he be doing to fulfill his responsibilities better?
I have also seen in him some puzzling contrasts. For instance, he has driven his wife away by being too immersed in work. Yet, when he meets the widow of a Latvian Major, he takes leave from work, and crosses borders illegally to help her. I wonder if its the same person being talked about, and the only rational explanation seems to be is that he has a strong desire to be needed. So as long as it is a damsel in distress, he can expend his energies and time saving her, but cannot work on a relationship with a woman who is safe and needs him only for emotional support.
I also find it interesting that since Wallander, a few troubled detectives have found their way on screen. (Detective Hardy from Broadchurch being one from recent times). Even those who love the dazzling Sherlock Holmes, are happy to see these real people struggle through detection and grapple with their personal demons.