Voyager by Diana Gabaldon

This is the 3rd book in the Outlander series.  It's a time travel, adventure/romance whirlwind of a story. Don't be thrown off by the 870 pages.  There isn't a spot in the book that drags. 

In "Voyager", Claire, now realizing that the love of her life and soulmate survived the battle of Culloden, makes the decision to go back in time and find James Fraser, as for the past twenty years her love for him has remained constant.

Leaving her daughter, Brianna, she once more hurls herself into the vortex of time to eighteenth century Scotland to begin her search for James Fraser, in hope of being reunited with her 'Jamie'.

This book tells the story of what happened to Claire Randall and James Fraser in those intervening twenty years. It tells of their ultimate reunion and rediscovery. With historical events as a backdrop and an unforgettable cast of characters, it regales the reader with their new adventures, as Claire returns to a still divided, turmoil ridden Scotland. Reunited with James Fraser, none the worse for wear, they seek to make a life for themselves. Their reunion is passionate but not peaceful for long. Jamie and Claire's efforts to save his nephew, Ian take them on a voyage, sailing the high seas all the way to the West Indies.