So the synopsis is a bit inaccurate because the female lead actually marries the crown prince in the first couple of chapters. It isn't an "engagement". So the romance that blooms between her and the prince's brother is a very clear cut case of *****ery.
So, uh, just be warned on that front.
As for the story itself... well it's exactly what it says on the tin, isn't it? One girl. Two guys. Messy love triangle ensues. The setup around that premise isn't half as interesting as the premise itself. If you're in that particular type of mood to read something that will inevitably leave you with bittersweet feelings at best than this story is good enough to scratch that itch. I can definitely give it a solid recommendation on that merit alone.
SPOILERS FOR THE ENDGAME BELOW
Personally, I enjoyed the beginning and the conclusion. After reading so many Chinese romance novels stumbling across this was a breath of fresh air. For once the cold asshole guy who always treats the female lead like garbage DOESN'T end up with her at the end of the day. It's so refreshing! The girl doesn't choose the guy who is always being a huge dick to her all the time, hooray! Seriously, just on that merit alone, I want to give it a straight 5/5. Unfortunately, the journey to get there is kind of... questionable. You have to close one eye so you don't see the big elephant call "*****ery" that is always in the room. If you can manage to do that it's a good time I think.