I finished it (Knight In Shining Armor).
Full spoiler for anyone who's interested.
Spoiler
Dougless is dating a man who's a jerk. They go on vacation out of the country, his daughter steals Dougless' purse, and they strand her at an old church. She starts to cry, and a man appears. He says his name is Nicholas, and he's from 400 years ago, and he came because she needed him. So they figure out that he died, and he was transported there at his death. Long story short, his wife had his brother killed so that he would inherit. Then she married him. But they didn't have any children, and she wanted a son to put on the throne, and he also wasn't interested in rising in the ranks politically. So she set him up for treason, then had him poisoned to make doubly sure. Then she had his mother killed. She remarried but it turns out she was barren. Nicholas is especially upset because now he's pretty much just famous for being a rich womanizer who committed treason. Dougless and Nicholas end up sleeping together, and saying they love each other, and then he magically gets put back in his own time. So she does some research to see if anything changed when he went back in time now that he knew he was set up for treason and by who (which is kind of weird since he was already dead in his own time, but....). And she finds that he didn't die from being poisoned, but he did die from execution for treason 3 days after that and still had a bad reputation. So she mopes around for a couple days. Then she gets magically transported back to his time, but 4 years before his death, so back before he even knew her. So she basically spends the second half of the book earning his and his family's trust. Then she warns him about his brother's death and was able to save him. She warned him about his son's death and was able to save him, so then he did have an heir. And then she was able to get him to call off his engagement (he didn't really want to marry the other woman, but he felt it was his duty because it would be good for the family). She told him to leave her a small painting of him and where to put it so that she could come find it 400 years later. And he had a little painting done of her. Then they slept together, and she got magically put back in her own time. So then she started researching and found that he had never married, he lived like 30 more years, his son survived to adulthood and had heirs, and he was famous for designing buildings and being sort of the father of modern medicine (because of what Dougless taught him). Then she went and got the little painting that he hid for her. Then she got on a plane to go back home to America. On the plane, she met a man who looked like him, and he sat next to her. She was kind of like, "Buzz off, buddy." But then he told her about how she reminded him of a painting. He told her he saw an old oil painting in an antique shop when he was a kid, and he saved up money until he could buy it, and he brings it everywhere. He showed it to her, and it was her painting from 400 years ago. On the back, Nicholas had written something like, "My soul will find your soul." So then she knew it was Nicholas' soul, and so she said she would go on a date with him. The end.
I ended up giving it 3 stars on GoodReads, which means "just ok" for me, although I think 2.5 starts is more accurate.