I actually found out about this drama via AvenueX's YouTube channel. While I disagree with most of her negative comments about this drama, I can understand why this drama doesn't have a rating over a 8.5.

Characters:
The female lead was married as a princess (episode 1), but engaged as the physician's daughter around episode 3; she broke off the engagement, but then got married to her sickly cousin just to treat him, solely because he was too shy to allow her to treat him without clothes on; but again, she broke that off too by getting divorced. The only one she liked was her childhood friend, who was a prince. While the characters don't drive me crazy, I still don't understand why she hated her husband so much, the one who she married when she was a princess in episode 1. Granted, she didn't ask for the marriage but as a princess, this is what came with the title, the fortune, and comfortable life. Her husband, at least in the first 19 episodes actually loved her, and did her a favor by marrying her sister, in order to protect her from their uncle. So, I would have liked for the scriptwriter to have either made his character totally evil (referencing the character the female lead married during episode 1), or given a better reason why the female lead didn't like her husband.

Directing:
The female lead actress, is a great actress. I know this because I've watched Good Bye, My Princess. However, in this drama, she acted with a, 'I don't really give a f,' kind of attitude throughout the whole drama. I don't like the fact that the director directed her to act this way. I believe the director should have directed her to act as a princess would have acted (e.g. a bit arrogant & privileged but strong willed), instead of a princess who is aloof most of the time.

Storyline:
The storyline is actually good, although not great. The reason why I gave this drama a rating of a 8.5, instead of a 10 for the story is because some of the scenes were not well crafted, and there are loopholes in the story. For example, somewhere around episode 2 the princess gets surgery and is turned into looking like the physician's daughter. I thought to myself, this is super unrealistic, and the scriptwriter and editor didn't even bother to come up with a logical explanation to why a ancient physician would be able to change the face of the princess, while in a cave. All she had around her head when she woke up were bandages, which btw, were loosely wrapped around her head... SIGH.

Editing:
Overall, I am enjoying this period drama thus far. I am currently on episode 19, but I did take a break to watch other dramas! For some reason the faces of both the female lead (same actress from Good Bye, My Princess) and the male lead (same actor from The Princess Weiyoung) look strange. I know that these dramas are often edited (e.g. lightening the actors skin to make it appear closer to the color white). However, the editing this time, in terms of changing their facial shape, was not done well. At one point, I even thought that they both may have had plastic surgery, which honestly there's nothing wrong with, but I concluded that it was just bad editing.