Thóra Gudmundsdóttir (fifth in the series) is also a ghost story, a horror story, and an entangled and engrossing investigation into crime and criminals.
Investigating on behalf of her legal office, Thóra Gudmundsdóttir goes to a secure psychiatric facility to meet a very twisted and unpleasant long-term inmate who wants to sponsor re-opening a case -- but not his own. It's unclear why, but he asserts that a younger man at the facility, Jakob, who has Down Syndrome, isn't guilty of the arson that's put him here. The investigation bumps up against more death and destruction, and although Thóra realizes she's being used in some way, there has clearly been a miscarriage of justice and her task is to prove it and rebalance the scales.
Brace for a slight resistance in the translation, as well as the protagonist -- although Thóra is clearly heroic in her choice to accept the case and investigate a series of horrible events, it's hard to warm up to her. It's her mission that's compelling, instead: to learn rapidly the laws around imprisonment of the disabled, to protect herself from the air of menace surrounding so many people in this investigation, and prevent the unpleasant and even evil aspects of the case from affecting her home.
"Noir" means black, and this one's steadfastly dark in subject matter; it's a good fit if you're a Kurt Wallander fan, isn't as extreme as The Girl With the Dragon Tattoo, and gives a persuasive look at social aspects of crime that need attention. It's not necessary to read Yrsa's earlier work, but if you're collecting Scandinavian or, more broadly, international noir, I'd recommend the full series.