I liked the character development over the course of the book and the way that the friendships formed and changed. Cassandra Claire does a really good job of descriptions for world building and made me feel like I was there watching the story unfold. Claire also has a way about telling the action scenes that makes it more interesting for the readers.
I personally hated the ending. It made me really want to read the next book but at the same time, I felt like I could predict what would happen in it. Honestly, the whole book was sort of predictable from the beginning to an extent.
Since this is the story of the kids of Tessa and Will's kids, it did have a very similar story to theirs in that James was almost the same character and he was also going through a love triangle with his best friend and Cordelia.
But overall, I love how the Shadowhunter universe interacts with other parts and makes constant references to the other book series she wrote.