This is the sixth book in the Outlander series by Diana Gabaldon.

The basic premise of the series is a time travelling heroine, Claire, who leaves post war Scotland and lands in 18th century Scotland, meets, falls in love and marries Jamie an ancestor of her 20th century husband. Early in the series Claire returned, pregnant by Jamie, to the 20th century but after her daughter reaches adulthood Claire finds herself pulled back to be with Jamie. She manages to convince her daughter that she’s telling the truth about the time travel and is planning on going back. Her daughter then not only follows but takes her 20th century boy friend along with.

By book six, A Breath of Snow and Ashes, the story has shifted from Scotland to the United States just before the Revolutionary War. Gabaldon crafts a story that becomes like a mural of early American life as she introduces and intertwines a broad range of characters to not only lend action and variety to the story but to paint a picture of history as it unfolds.

While it would be helpful to read the rest of the series, you can read just this book and get enough of a handle on what has happened previously to understand what is happening now. The end of the book has been left open to either end the series or produce at least one more before Jamie and Claire need to die.

One more exploring the Revolutionary War would be my vote. This is a series well worth reading