I read this book probably in the 90's but it could have been 1980's-2000's. About a man who was selectively bred by advanced race without knowing it. A woman comes to earth to train him to use psychic like powers, they go back to her world and get separated and he starts out traveling by mountain bike, then changes himself into a godzilla like creature to be able to travel safely. When hi finds the woman and her people he finds out it was all a test to train him. I think that's where first book ended. Don't know if anymore were written.