The Purity of Vengeance, by Jussi Adler-Olsen

Adler-Olsen creates some very creepy villains.  Racial purity engineer Curt Wad's awfulness is compounded rather than mitigated by his obsessive love for his comatose wife.  The very flawed members of Department Q, Carl Mørck and his assistants, Assad and Rose, and the often quite silly and sometimes quite hair-raising situations they get themselves into, keep the books from lingering too long in pure horror.  According to the publishing notes, Adler-Olsen's father worked briefly at the Sprogø home for fallen women in the dark and dreadful period of Danish history when eugenics was considered a reasonable approach by some.