Diana Gabaldon's Outlander series is my favorite, too. My mom started listening to them on tape (yes tape) when she had her knee replacement. Since I had small children in the house, listening to tapes wasn't an option, so I started reading the books.. (They are really large books, by the way!) Couldn't put them down. Love every one. I've always hated coming to the end of a book and wondering what happens after the book ends. With this series, you can follow them for 30+ years, see their children, and grandchildren. It's an epic fantasy romance. I borrow them from our local library which is just 6 blocks away. I've been known to read one in less than 10 days, which is quite a feat for me. Many of the books are nearly 1000 pages.
If you are going to listen to them, be sure to get the unabridged versions. I once borrowed Outlander on audio for a road trip I was taking by myself, and there was SO MUCH missing from the storyline in the abridged version. If I hadn't already read the books, I wouldn't have noticed. The typical unabridged audio has 38 disks and 45 hours of listening time.