Outlander — Diana Gabaldon

Since Outlander's publication in 1991, readers can't seem to get enough of the time-traveling Claire Randall and her Scottish husband, Jamie Fraser. The books have topped many favorite romance novels of all-time lists and have since been turned into a popular TV series for the Starz network. The series follows the exploits of Claire, Jamie and their friends and relatives from eighteenth-century Scotland to Colonial America and the American Revolution. This genre-bending series can be classified as historical fiction, time-travel, romance, suspense -- the books have it all.

While the first couple of books focus on Claire and Jamie, later books add a wider cast of characters including their daughter, Brianna, and her husband, Roger. The Outlander universe also contains a series of mysteries featuring Lord John Grey, a character first introduced as a prison warden in Dragonfly in Amber.