I rather enjoyed it, although it isn't my favorite of her books. Trifle dated for sci-fi, of course.
Young woman wakes up in what appears to be an insane asylum, caring for a strange man. She slowly regains her sense of self and realizes that not only is she not home, she seems to have a new body (old scars and marks are gone, different skin tone (more olive or tan, I think), and so on) Has to learn the language and at some point realizes she's not on Earth anymore. And then her charge gets a visit that implies he's a very important man and perhaps shouldn't be there. So she decides to try and free him and hopefully herself as well.
See if you can get it from a library. Interlibrary loan is your friend in these cases.