I feel like it's easier for me to explain what didn't work for me in this book than what did. Cruel Beauty is, as many other reviews will tell you, basically a retelling of The Beauty and the Beast mashed up with some Ancient Greek mythology. It takes place within a lost part of Romana-Graecia, Arcadia, which was cursed and locked away in its own pocket universe by a vengeful demon 900 years ago. The protagonist, Nyx Triskelion, was promised at birth to one day marry this exact demon, in exchange for her twin sister Astraia being allowed to live a normal, happy life. Nyx has spent her short life thus far being trained for this event, and when she arrives at her husband's cursed castle, it's with a mission: to destroy him, and probably also herself, to break the curse keeping Arcadia isolated. Once she gets inside, though, everything gets a lot more confusing and complicated.
So... where do I begin? I will say that this is not a book with strong world-building. Arcadia is a real part of Greece, and a lot bigger than the “one village and a castle” than it seems to be in this book. We learned a lot about the differences between the gods worshipped by the nobility (Zeus, etc.) and those worshipped by the peasantry, and a bit about their festivals and funerary rites. What wasn't really that clear was the magic system that kept getting referred to (Hermetic magic...?) – how was that supposed to work? what was it supposed to do? – or who the demons were that were screwing over Arcadia's people and how they all related to each other. The mystery is a large part of the story, but it's never truly answered, imo.
Then there's Nyx herself. She's had a rough upbringing, having been raised to be a sacrifice to the Gentle Lord, and is full of resentments. In the enchanted castle, she has no idea who to trust and ceases to be sure whether to follow through on the mission she's been trained for, or whether something else is a better idea... which seems to lead to the outcome that she changes her mind every five pages. Neither of these things make her a bad character, and certainly not an unrealistic character, but it made it very hard to know what I was supposed to be hoping for. Sometimes plot developments would happen that you'd think would mark a significant turning point in the story, only for them to be completely disregarded. I spent so much of this book confused.
A large component of this book is the romance, of course, but I even found this confusing. I just didn't feel like I'd seen why Nyx started to fall in love... instead, I just had the book telling me that she had indeed fallen in love. So then I was like, well OK, I'll just accept that these two are in love now. (To be fair, it was the kind of dark romance that I really wanted to be able to enjoy.) But then the book threw a huge curveball at me by allowing Nyx to return to her family home when we'd previously been told that could never happen, and having Astraia tell Nyx she had to follow through and kill Ignifex, and out of nowhere Nyx decides she loves Astraia enough to do exactly that, even though so far there'd only been bitterness and resentment between them?! Look, overall, I just don't think this romance had a lot of depth.
The ending had its fair share of confusion, but I actually found it one of the most enjoyable parts of the book. Only here did I really start to see the sisterly love that was supposed to exist between Nyx and Astraia (although, given it was basically in a parallel universe, I don't even know whether that bond existed in the original universe), and the world started to seem a bit more fleshed out. Plus, after all the confusing "oh, so I can have this thing?" "NO YOU FOOL!" shenanigans, it was nice to see Nyx FINALLY just break a curse and have a seemingly happy ending.
This review probably sounds mostly negative, but it's really more that I found this story confusing. When I shrugged my shoulders and gave up on trying to understand things, this book was enjoyable enough. I liked the duality of Ignifex (the Gentle Lord) – the malevolence but also the tenderness. Shade was an interesting character, too. I just kind of wish the story around them – the web of curses and such – had been better explained.