Fantasy. Boy is sent on errand from a farm, awakens from battle and has become King but has amnesia.

[Jennifer]

A boy is sent on an errand from a farm. He awakens from battle and has become king but the last thing he remembers is leaving the farm to start his journey. He is older and has become muscular. A few people know he doesn't remember and tries to fake it.

[Kris]

Jennifer, around what year did you read this book?

Is this book for kids, teens or adults?

What are the fantasy elements?

I copied a few book details to the topic header. Feel free to edit it.