The setting of the book takes place in many different places, but a continuous place for the killers to show up is at humongous houses owned by rich families. In Sansfrancisco, California i'm sure you can picture how large the houses are for those that are well of money wise. The author describes the houses with flourishing gardens, vibrant colors, and a knack for catching anyones eyes. Another main place is the cheif detective's, Lindsay, apartment where her and her boyfriend Joe have just moved in. Their apartment is small and cozy, but they are very comfortable with it and appreciate what they have.
If the book took place in a different setting it could possibly make the connections with the location suffer. The villains are burning down houses of rich people, and this is partly because California has so many forest fires. Where it is also shows that even where crime is worse than usual, good police are fighting to stop the criminals.