Nightkeepers (Final Prophecy, Book 1) By Jessica Andersen

In the first century A.D., Mayan astronomers predicted the world would end on December 21, 2012. Modern scientists say dire solar flames and magnetic fluctuations will all occur on that exact day. In these final years before the End Times, demon creatures of the Mayan underworld—The Makols—have come to earth to trigger the apocalypse. But the Chajinal, descendants of the Mayan warrior-priests, have decided to fight back. In Nightkeepers, a Makol uses a lost rite known as The Godkeeper to call a demon to earth. During the ritual, a sky god attempts to possess the demon’s human sacrifice, a narcotics detective named Leah Ann Daniels. The rite is unsuccessful, but gives Leah magical powers, and strands the god between planes. Warned by a cryptic message from an ally, King Jaguar Striker arrives just in time to save Leah…but is exiled when he breaks Chajinal law. Leah and Striker must bond together to defeat the embodied demon and gain support of the Chajinal army—all before the next solstice, when another demon will try to pass through.