I have watched quite a few historical K-dramas, and this is another strong one.
The story does have the familiar elements of court intrigues, paranoid king, sibling rivalry over both the throne and love (kind of), time of separation, and loss.
The synopsis here on MDL is a bit misleading, or should I say: not as descriptive to the actual events in the drama. It revolves a lot more around everything happening before she became Queen.

The series starts off almost at the end, so we know tragedy will strike. It then takes us back to the beginning of the main couples' story, with a happier mood, but with events building up to the dramatic future. The young cast was brilliant! Kudos to all of them.

As for the adult cast, I thought Lee Dong Gun portraying the elder brother (king Yeonsangun) was absolutely superb. Everything from his facial expressions, the look in his eyes, and tone of voice – this was really strong acting. Even if he played an un-likeable character, you still got some sympathy with him, much because of Lee Dong Gun's portrayal: He managed to show us his character's feelings of hurt and betrayal.

(FL) Shin Chae Kyung portrayed by Park Min Young is also impressive. Her acting is consistently on-point.

(ML) When it comes to Yeon Woo Jin who played Yi Yeok / Nak Chun, he was mostly strong. There was a few instances though where (in my opinion) it looked like he was suppressing a smile instead of crying.

I did search up the history around King Yeonsangun, King Jungjong and Queen Dangyeon after completing the drama, and if Wiki is kind of reliable, my understanding is that the drama is loosely inspired by historical persons, not necessarily by historical events.