If you've read much historical romance, then you've most likely heard of Outlander by Diana Gabaldon. Somehow, I hadn't read it but my (future) brother-in-law bought it for my birthday, so now I can say I've experienced Jamie and Claire.
Here's the description via Amazon: English nurse Claire Beauchamp Randall and husband Frank take a second honeymoon in the Scottish Highlands in 1945. When Claire walks through a cleft stone in an ancient henge, she's somehow transported to 1743. She encounters Frank's evil ancestor, British captain Jonathan "Black Jack" Randall, and is adopted by another clan. Claire nurses young soldier James Fraser, and the two begin a romance, seeing each other through many perilous, swashbuckling adventures involving Black Jack. Eventually Claire finds a chance to return to 1945, and must choose between Frank and Jamie.
I think the whole two men in her life thing threw me off from reading the series but it truly was an interesting, good read. It was long and full of adventure--and I was actually distraught, thinking there wouldn't be a good ending. It's easy to see why this series is a classic.