Yi San is a highly addictive historical epic that everyone should try watching.
It is based on the real-life highly regarded king of Joseon (Korea) but with the addition of a bunch of fictional character and plots to make it more entertaining.
It starts when Yi San is a child trying to save his farther (crown prince Sado) from being killed by his grandfather and goes all the way through his life until the end. That's 77 hour long episodes which are nearly all exciting.
It has thrilling action scenes, heart-warming love interests and compelling characters who you will miss when you are done watching it. I never cry and basically have no feelings at all about anything but Yi San's love story almost brought a tear to my eye (although that may have been my contact lenses).
I would recommend this show to anyone who can read. Even my wife got into it and she particularly hates historical epics with subtitles, normally. She even asked me to put on that "good Korean thing" on one occasion. High praise indeed!
If you liked shows like Warrior Baek Dong Soo, Jumong, Kingdom of Wind and Iljimae, then you will love this. It has a lot of the same characters as in Warrior Baek Dong Soo btw. If you didn't like those shows, time for a trip to the doctor to see what's wrong.
When I hear people talking about how good shows like "Game of Thrones" are, I always think, they only like it because they have never seen any of the Korean historical drama. They are soooooo much better.
I would have given YI San a 10 out of 10 except I found the ending to be unsatisfying but history is history I guess. Still, making 76 great episodes out of 77 is not bad!