I am hoping for your sake that you didn't consider their relationship healthy. Hopefully you are asking for books so that you can get the bad taste that is FSOG out of your mind. But if you aren't, you still need to read this books:
Hunger Games: A series with a REAL romance, among other things;such as sacrifice, bravery, humanity, the value of human life, and other important themes can be found here.
You might try Kristen Ashley. Either "Knight" which has a great anti-hero or "Mystery Man" which is more of a romantic suspense chock full of emotional angsty-ness. Ashley self-publishes and could use an editor, but has a crack-tastic readability similar to FSOG (I think). Other books I've enjoyed if you want a contemporary romance type: "Ride with Me" by Ruthie Knox, "Gateway to Heaven" by Beth Kery. "The Marriage Bargain" by Jennifer Probst is also getting a lot of good reviews (I thought it was entertaining, but a little silly). "Bared to You" by Sylvia Day is really good as well (to me it read like a re-write of FSOG with a more mature female lead.) If you want the BDSM edge with romantic plot-arcs you could check out Cherise Sinclair's Masters of the Shadowlands, Kallypso Masters "Masters at Arms", Shayla Black's "Sweet" series. If you want more engrossing historical fantasy, Jacqueline Carey's Kushiel's Legacy books are fabulous --they start with "Kushiel's Dart".