I really recommend this drama to anyone who loves sageuk dramas!
there's action, revenge, romance, hidden identity and overall a great plot that doesn't drag at all.
this has become one of my all time favourites.

It's long, however the 108 episodes are only 30 minutes long, so there are 54 normal 1h long episodes. it's still long but significantly shorter than 108 episodes. (Apparently this was actually scheduled to have 120 episodes, but was shortened. Considering how much I love this drama I probably would've liked to see what they would've put into those other episodes.)
I binged the whole thing in 11 days.

Music:
the OST is really good, however you can't find the whole soundtrack T_T

as for the romance:
- Myongnong and Solnan are the cutest couple! it's sweet seeing two people fall in love for the first time. There love is really innocent and sweet. there is some angst towards the end, but in it you can see how much they're in love.
- Jinmu and Solhee as bad as they were good for eachother, and I did like some of their scenes.
- The first 10 episodes are about the parents arc and how they fell in love and everything. I was invested in their story as well.
- then there's also a 4th couple with the guy from the princess' man and a friend of Solnan's and they were nice as well.

Characters:
- solhee is the absolute worst! sometimes I felt sorry for her, but she brought everything upon yourself and is pretty narcissistic! she was always a rotten apple, however I did like how things ended for her.
- Jinmu was pretty sleezy and was one of the villains, however I kind of liked his character in the end=his character development
- The Queen was super sweet. finally not one of those scheming queens!
- chancellor yon who was a villain, had some kinda cute moments with his folding origami or his weird/funny sounds he makes.
- I like that the characters are well written and have motives etc.

Acting was really great! I was impressed by all the crying in this drama because it felt so natural but also sad during the dramatic/death scenes.

The ending was happy for me (both couples) it's maybe a bit open, however at least you know they ended up together.

the last scene of the drama where the subaekhyang tree flowers and the blossoms are floating around was nicely made.

This was such a wild ride! so much happened in these episodes despite them being shorter than usual.

History:
some of the characters did actually exist. It's debatable whether princess subaekhyang actually existed or not.

Overall I'll give it a 10/10 and I really recommend it!