As an initial disclaimer I'll admit that I didn't have an ideal reading experience: I had to listen to the audiobook at 1.5x speed in order to finish it in time before the next person's turn to borrow it.
That being said, I didn't like the book. The best things about the trilogy (the fantasy magic system, the originality of the historical/geographical setting) aren't anything special by that point, after dozens of hours of listening. There's nothing really new in the third book, Kuang is just capitalizing on the world she's already built.
Plot-wise I got sick of the mindless fighting (I already had enough in the second book). The overarching story comes to an incredibly underwhelming climax ("oh wow we won the war"). Some plot elements are plain weird (for example: the super-powerful "Trifecta" characters, who received a huge backstory over the entire trilogy... just boringly die somehow). The main character's story arc doesn't go anywhere, and the rest of the characters are relegated to decor. It feels like Kuang gave up on the plot midway through writing the book and quickly tied up the loose ends.
I only finished the trilogy because I wanted the satisfaction of knowing how it ends. Bad luck: the book concludes on a frustrating open ending.