It has the typical conspiracy, treason, revenge plot that you would expect in a period drama. I am glad that it is only 20 episodes (I watched on Netflix) long so not as draggy as those that are truly 40 episodes and above. I can't pinpoint what exactly made me stay throughout the show. The costumes were beautiful , especially Prince Dowon's. I had favourite characters (and the actors who played them):

Prince Dowon, Yi Rim - Cha Eun Woo did really well in this drama. I think he is a good actor, he was believable. He went from being silly, in love, serious. He cries prettily too LOL. Kidding aside, I think he did well and does not suck as an actor like some of the comments I've read here.

Goo Hae-ryung - Shin Se Kyung, I like her character here. I like her banter with Prince Dowon and how she always manages to stump him. I like how she doesn't play innocent and dumb. In her subtle way she shows how in love she is with Prince Dowon - and his reactions are so cute. Oh I skipped all the parts wherein he had to have an arranged marriage with someone else - I didn't care, didn't want to know and didn't want to go through all that.

Officer Min Woo - such a straight arrow. He somehow gave me comfort that no betrayal to the historians would go past him.

Crown Prince Yi Jin - I liked his smile what can I say. I like how he treats Yi Rim and was super scared that he would turn out to be a villain - glad I was wrong,

Heo Sam Bo and the 2 court girls - a fun trio

The Historians - what a wacky bunch. I thought they would be bullies and would make the female historian's live hell throughout the show. They actually turned out to be a loyal lot where it counts. One historian, Hyun Kyung Mook did annoy me ;-/

All in all it was a good watch. The ending was fitting. I did wish for more though........ :-)