The Last Killiney, the first book in The Ravenna Evans Series.

On holiday in England, Ravenna Evans begins to recall her past life as an eighteenth-century Irish viscount's lover. When she is swept back in time to relive this affair (along with Lord Killiney's very unwilling modern counterpart), she learns that living in the past isn't all fun and games, and that history can't always be changed to one's liking.

In that doorway there stood a young man, no older than thirty, whose russet-brown hair made her senses reel.
     Miss you, love you, you don't know how much.
     How familiar, that gait of his, the way he carried himself as he crossed the room. It was as if he knew everyone, yet took no one for granted. He buttoned up the last button of his faded jeans as he joined his friends at a table near the door, and his expression was one of beguiling innocence. He'd been in the men's room. His friends railed at him for his deliberate act of laziness, coming out of the toilet with his trousers still open, but he only seemed to revel in their scolding; he grinned when the girl at his table slapped his hand - such attention from a woman delighted him, Ravenna could see it.
     She watched as he took the unlit cigarette from the girl's mouth and proceeded to fumble with it, searching behind the Guinnesses for a light. It was then Ravenna noticed the true nature of his mood, for in the act of lighting that smoke, his grin faded into weariness. His friends went on with their discussion around him. Still, he didn't notice. He seemed to have tuned out their words completely as he played with the smoldering end of his smoke, and despite the dark, neglected hair in his eyes, she could easily see the painful blue of his listless gaze...the blue she knew so well, blue like china, like the color of the ocean after a storm, and how many days had he lost to the sea?
     His face was haggard, shadowed with whiskers. His hands were sore, but when he laid them on her, looking at her with such reverence and need, they hardly mattered, those cuts and blisters. With his grin barely concealed, he brushed against her deliberately while the sailors worked around them. His touch lingered at her waist, her hips, and making certain the captain was well below decks, he whispered in her ear with the most loving voice she'd ever heard: He'd die without her, did she know as much?
     His tired laughter rang out over the music, and the sound brought her back immediately. Velvet, Irish laughter. As she stood there in the midst of the crowd, watching him whisper in his friend's ear, she felt a wave of warmth wash over her. Just looking at him made the visions struggle at the doors of her subconscious. What would happen if she approached him? Would her knees shake? Would she ever get over that mischievous grin?