This is an excellent read. I'm not sure whether to classify it as more alternate universe or sci-fi, but it's definitely an excellent read. (Riptide calls it AU.) 
 We're immediately drawn into the strange intrigues of the island known as Santuario, and then into a murder mystery. The inner political workings of the island slowly come into focus over the course of the story as the main characters, a policeman from Santuario and an investigator from the mainland, walk the fine line of asking questions while trying not to make enemies of the powers that be, the familias. 
 There are several levels to this story. One is the differences between the Santuarians and the Skanians, evident in the relationship between Alex and Bengt. Then there are the inner-workings of the familias and their Securitas forces (private muscle), vs. the djeti (non-familias) and the policia, which can only work at the leisure of the Securitas AND the Skanian ICE. Then there's a political movement to free Santuarians from the oligarchy of familias and integrate them with the democratic Skanes. Then there's Alex and his own history to overcome. 
 If you're looking for tension, interesting world-building, and a good mystery, this should be right up your alley. Alex is a loner who somehow lets Bengt inside his walls, and Bengt gets an crash course on the inner workings of a culture he understood nothing about, while slowly and unintentionally falling for the man helping to educate him. The story switches back and forth between their points of view as they come to understand one another slowly, past the cultural differences. 
 The Santuarians use quite a bit of Spanish in their way of life and speaking, so expect to see many Spanish words and phrases, though all are given proper context and are easily understandable. 
 This was a highly enjoyable read. 
 4.5 stars (rounded down until I determine rereadability).