The Guinevere deception
(Book)

Sent by a banished Merlin to protect King Arthur, a sixteen-year-old impersonating the deceased Guinevere struggles to fit in at Camelot where the magic she practices is banished.

Princess Guinevere has come to Camelot to wed a stranger: the charismatic King Arthur. With magic clawing at the kingdom's borders, the great wizard Merlin conjured a solution-- send in Guinevere to be Arthur's wife... and his protector from those who want to see the young king's idyllic city fail. The catch? Guinevere's real name-- and her true identity-- is a secret. She is a changeling, a girl who has given up everything to protect Camelot. Arthur's knights believe they are strong enough to face any threat, but Guinevere knows it will take more than swords to keep Camelot free. But when your whole existence is a lie, how can you trust even yourself? -- adapted from jacket