Goddess of Legend. by P.C. Cast (Goddess Summoning Series)
Isabel, a world-weary photojournalist, is grounded back home in Oklahoma, when her car plummets off a bridge into a lake. Struggling on the edge between life and death, shes miraculously saved by the Water Goddess, but with one tiny caveat: Isabel must travel to another time to seduce the legendary Lancelot du Lac away from Queen Guinevere. Simple. After all, the handsome knight is a dream for any woman in any century. Unfortunately Isabel is the one whos seduced - by the soulful eyes of the wise and soft-spoken King Arthur. But for Isabel, a deal is a deal. Now, the King watches as fate takes from him the mysterious beauty he has come to worship, knowing all too well that any interference on his part could destroy the kingdom he loves.