The Hidden Iceland series by Ragnar Jónasson

During a hot summer four friends visit the isolated island of Elliðaey, but only three of them return. Detective Inspector Hulda Hermannsdóttir at the Reykjavik police is sent to the island to investigate and soon finds haunting similarities with a previous case – a young woman found murdered ten years ago in the equally desolate West Fjords. Two young women, once best friends, both found dead in isolated locations. Is there a patient killer lurking in the barren outskirts of Iceland?

Read more