The Song of Jonas (Paperback or Softback)

The year is 7,001 CE and Jonas Neferis has never been to Earth. He's never seen a dino-lizard, never fought demons or skeleton warriors, never talked to god-like celestials, and definitely never taken advice from a time-traveler from the future.
 
Jonas is an eighteen-year-old newly graduated Intergalactic Special Agent living on the Ashtar Command Center, a giant space station in the center of the galaxy. He is a Shastra, which is to say a humanoid with the head of a jackal and the body of a human being. Given the important mission of traveling to Earth to research another agent's disappearance, Jonas encounters many new and strange beings, their ancient golden cities, and even attends the archery tournament for the championship of the entire solar system.
 
But soon his mission is turned upside down by an ancient Shastra hermit and his lovely assistant. Their task is to warn Jonas of the appearance of an ancient evil to Earth, an evil from the Underworld, and convince Jonas to accept a special role in the current age to ensure any hope of Earth's survival.