The cold-case mystery that this novel centers on is not that compelling. You'll want to keep reading mainly because of the interesting dynamics between the detective partners Robin and Strike and between them and their families.
This is the 5th book in the series. Cormoran Strike is asked to help find Margot Bamborough who went missing in 1974. He is visiting his family in Cornwall and most of the book is about introducing Strike's family members. This book is a bit long but does further the relationship of Strike and Robin. I'm looking forward to the next installment to see where their relationship is going next. Robin herself is also juggling a messy divorce. This complex case has leads that include tarot cards, a psychopathic serial killer and witnesses who cannot all be trusted. They learn that even cases decades old can prove to be deadly. It's best to start with book 1 if you are interested in reading this series.