The highest praise I can give to a book is that it was coherent and satisfying. This book (and series as a whole) is both of those things in spades. I love it.
Despite being a prequel series to another series, which confirms that Vielle more-or-less succeeds, this book maintains such high tension the entire time. There were moments that I was scared to keep reading because of how invested I was into the characters and what was happening. The stakes are so infinitely high (only the fate of every living thing) and the death toll staggering.
I love that this is a story of becoming. For all that Vielle rails against it as much as she blesses it, the idea of a Prophesy with a will of its own is so compelling to me. Especially in a prequel series where so much is preordained, the way the Prophesy works through Vielle and shapes her just works so well. It's the idea of a 'chosen one' taken to the absolute extreme.
I love that it is a story about the necessity of trusting one another and forming alliances and bonds with people, even if they look and are different from you. It's about freedom and equality and democracy and despite how brutal the battles in this book are, it's also about hope and clinging to it with your fingernails even when everything seems bleak and hopeless, and about fighting for the future and for peace.
And the romance! There was honestly a bit less of it than I wanted it but everything that was there felt so true to their characters. Of course these two are Soulbonded, of course they are two halves of a whole, of course this whole thing would not have worked if it weren't for the two of them being exactly what they are. I love that they exist as a pair, separate but parallel to the Prophesy, as if it couldn't have happened any other way. Of course I wanted to see more of them together and wanted a bit more explicit confirmation of their feelings, but also there were still so many great moments of them getting to know each other. I still do think this is one of the best enemies-to-lovers romances I've read even if we don't really get a whole lot of the 'to-lovers' part. Bound by magic, forced to work together, forced to recognize your equal in cleverness and ambition, I mean, what more can you want? (if this were another genre I would have wanted them to kiss but alas)
My biggest complaint is that it's that I really wish there was a map that labeled the Flower Forests and major locations of the book. I was able to roughly keep track of where people were but I still often forgot where Ceoprentrei, etc was in relation to other locations which was kind of frustrating. Related to this I would have appreciated some sort of glossary at the end because there are a lot of new words and it can get confusing quite quickly. (Note to self: deosil is right, tuathal is left, I think).
You could argue that the ending is a little rushed and I would probably agree. I think I would have liked a little bit more to connect the final Great Working to everything else. As much as I love the dragons, I feel like they should have been more obviously connected to the Great Working as well, since it is the last hurrah of the book and the whole series is named after them. While there are many plot points that come together so smoothly its beautiful to watch, there are also a decent number of plot points that fizzle out in a kind of confusing way or that suddenly arise out of nowhere. (In particular the thing with Shurzal's plan and the fact that Vielle is called High Queen in a lot of the excerpts but the origin of the name is never explained in the book, they only ever call her High King) That said, none of these things impacted my enjoyment of the book while I was reading it, they only bother me in hindsight.
These books are definitely not for everyone, they're long and dense, with lots of really long names, BUT I love them so much. The Obsidian Trilogy has been my favorite book series for a long time and now this one has joined it.