Here is the description from Amazon. They do a better job than I do. :)
Shana Abé has entranced countless readers with her passion-filled novels of adventure, intrigue, and romance. Now the author of The Secret Swan delivers a gift from the sea: three hauntingly beautiful tales connected by a legend, a locket, and a love beyond time.
531 a.d.: The tiny island of Kell is said to be enchanted, inhabited by an extraordinary creature who comforts shipwrecked sailors passing into the next world. Prince Aedan of the Isles believes in no such nonsense—until he awakens on Kell itself and meets the sensuous siren who rescued him from the sea.
1721: Ronan MacMhuirich, Earl of Kell, is the target of an unlikely assassin: Leila, a mysterious woman from an exotic land. But his irresistibly beautiful would-be slayer is in just as much danger as Ronan when she falls for this man with a magic of his own.
2004: What do you do when you inherit a Scottish island you never knew existed—and find yourself pursued by a handsome stranger who wants to buy it from you? That’s what happens to Ruri Kell when she accepts Iain MacInnes’s invitation to visit her birthright, and listens to a proposition as sinfully tempting as everything else about him.
Three seductive love stories, three passionate couples, all linked by one of the most romantic myths of all.