The Journey (Guardians, #1)

Following his involvement in a car accident, Daniel Graham wakes up in the land of Eden. He barely manages to crawl out from the wreckage, before he is ruthlessly hunted down by a dragon and its blood-thirsty rider. He is rescued by the Guardians of Lost Souls, a group of knights that were sent there to protect him. Now, they must journey together to the ruins of an ancient city, in search of the magical gateway that would take him back home.