It's a drama like no other. It's unique and it's fast paced. You certainly don't get bored and the story is extremely unpredictable. That is both its greatest strength and weakness. It really keeps you on your toes but since it's constantly fast-paced, it also tires you out. I needed several breaks - not because it's bad but because there was so much happening that I needed to recharge. Also heads up, because this drama will also require some brainpower for you to understand why and what is happening, so it's not something you should watch on the side. I saw many people being confused and dropping/disliking the drama because of that. Many perceived "plot holes" actually make sense when you pay enough attention. Not to say that there are no plot holes whatsoever, but it's not nearly as bad as some people claim.
I'm extremely conflicted on the romance. It happened extremely fast (and I honestly didn't understand why he fell that hard) and these romantic moments seemed quite unfitting in certain moments. The ending also left me feeling conflicted.
But overall, it's so unique and different from any other drama that it's definitely worth a watch.