The last few years I have read a few books that mix the supernatural with a private detective. Most do an okay job of it. However, Hostile Takeover crafts the world-building to make one of the best supernatural detective tales I have read.
Bellamy Vale is a private detective that has links to the supernatural world. Many centuries ago humans banished magical creatures to another world. Small portals allow them to access back to earth. Most humans will not see the supernatural due to camouflage but Vale can.
A seemingly random murder pushes Vale into an investigation that unravels a conspiracy. This conspiracy is one that could bring about the end of the world. Some members of the supernatural world want to return to Earth.
Hostile Takeover is book one in a trilogy. Trust me if you pick up book one you will want to get all three right away.