I like Indridason’s latest crime series for what it says about Iceland during the Second World War. Until now his stories, involving the exciting exploits of Inspectors Erlunder and Sigurdur, cover a modern country as it grapples with bigtime crime, with only veiled references to a distant past. Stepping back into the past allows this very formidable novelist the opportunity to deal with a host of interrelated societal issues back then that Iceland still wrestles with today: Nazi infiltration, foreign occupation, and the preservation of culture to name a few. As “The Shadow Killer” unfolds, the two cops assigned to solve a vicious murder quickly learn that there is a serious conspiracy afoot to cover up something more sinister than ever imagined. The reader will be taken into some of the more obscure parts of this island as these two gumshoes chase down all kinds of leads in search of the truth. In the end, it will not be as simple as pinning the crime on one perk, because, as we already suspect, Iceland is such a counterintuitive enigma of social layering that the shadows of its troubled and colorful past never quite disappear. This complexity is what makes a very mentally stimulating exercise in joining the forensic dots.