I've only seen about 5 minutes of it and chose not to watch it. However, that is mostly because I read the Outlander books (and enjoyed them) and already know what the characters look like in my head, which is not matched by what is on the screen.
FWIW, I've never been able to watch the Harry Potter movies either. :)
That said, there is a decent amount of history in the books - I certainly became much more interested in Scotland's history after reading the books, and the author did her research. There is also sex in the books, but I don't think it's overdone or distasteful. I also would not call it science fiction or steamy romance. It's sort of a weird mixture of history, romance and a titch of fantasy in there. Maybe historical fantasy might be the right genre?
If anyone likes the Outlander books, you might enjoy reading books by Susanna Kearsley. She is a Canadian author who writes historical romances with a bit of the supernatural thrown in. She is a wonderful writer and an incredible researcher. She has several books based in Scotland and I am re-reading them now before my upcoming trip. One of them - The Shadowy Horses - takes place in Eyemouth. And three of them - The Winters Sea, Firebird, and The Vanishing Day - are about Scottish history involving the Moray family. The Winter Sea takes place at Slains Castle and Cruden Bay (with one quick visit to Peterhead), and was the first book of hers that I read. If you are interested, she offers the chance to read the first chapter of her books for free on her website. And she does not have gratuitous sex in her books, if anyone is interested. :)