I feel very neutral about this drama.
Not my first historical drama and probably I haven't watched many of these but this definitely didn't make it as a favorite one, not even close to @Moon Lovers: Scarlet Heart Ryeo that's my absolute favorite.

As I said, if the directors would go with a happy ending anyways, they should've made it happier.
In my opinion, it was very nice how their love and affection started. I'm not referring to the times when they were children and didn't know they were helping one another, those were such beautiful moments. I'm talking years after when they met and she didn't know he was the Crown Prince and spoke casually (the drama includes fictional parts although based on a true story) and that caught his interest and he was slowly starting to feel more than just interested in her.

NOW THIS IS WHAT, IN MY OPINION, THEY SHOULD'VE WORKED WITH.
Why? Cause the description of this drama is all about the strong female lead, how she is educated and well mannered and righteous and has a talent for words and judgement. This is what initiated the sparkles of the love story and what they give us is a hot and cold female lead which I understand cause she wanted to be more free than a concubine could ever be. And it makes sense... she kept pushing the prince away for this exact reason and she ended up getting fired as a court lady so she went to live and serve elsewhere and kept transcribing books and making money out of it. That made her happy, she was free to make her own decisions.

Yet again, she went back to the palace out of her love for him. Cause I doubt she went there to serve his concubine. It was actually a dumb turn on the story line. So she chose to go closer to her lover, yet kept rejecting him, not showing him her real feelings. She would just stay in her house (which was very picturesque btw ) waiting for him to come visit. I really disliked this. Where was the fun, careless, energetic young court maid the prince fell in love with? They were in love ffs, we could've seen so many happy scenes from during the pregnancy, I imagine her being his right hand, helping him ease the weight in his shoulders. I imagine her being his safe and happy place more than they could ever depict in the drama. It was just too much focusing on the serious parts of this drama. I get it, they played a significant role but were they really THAT NECESSARY?

Anyways, something else that really made me feel rushed. THE DOUBLE STANDARDS
So just because we're talking about the Royal Secretary and he is the King's childhood friend, anything can be forgiven. No matter how many plots he created, how many people he bribed, how many people he hurt and killed. Yet, if a court maid were to fall in love and give herself to a man, death was the punishment and there were no exceptions. Excuse me now?

All in all it was good, the ending of each episode made me want to hurry up and check out the next one.
It kept me interested but I could feel something was missing. The actors did an amazing job. I literally checked this drama out because of Lee Jun Ho as I am currently enjoying him in King the land. The FL seemed talented as well but I couldn't always help it with her scenes.
Lee Deok Hwa who played the King; I actually thought a few times that he was probably the most likeable King in all the dramas I've watched so far. He is truly something else. As per the OST, I will have to check them once again. I don't remember anything in particular and as per rewatch value for me, I wouldn't go back it.