Over the past few months I’ve been reading the excellent Dublin Murder Squad novel series by Tana French
Unlikely most crime fiction, each novel is told in a first-person point of view of a different detective (except The Secret Place which is half flashbacks told in third person). However, the protagonists aren’t isolated - for example, the main character in The Likeness is the partner of the lead in Into The Woods. And the lead in Faithful Place has a significant role in a couple of the other books.
Each story has a crime that has a personal connection to the detective - they all end up changed in some way. And the stories don’t have happy endings that are tied up in a neat bow.
However, the main draw is the writing. I really felt engaged with the characters and plots and have read them all at a rapid pace (at least rapid for me lately).
Finally, from a Role-Playing Game point of view most of the books have ideas that you could steal for investigation or horror scenarios. Why is there a large animal trap in the attic of the house where a murder occurred? What actually happened to those kids that disappeared in the woods? Why does the murder victim have the fake identity of an undercover cop?
