I reread the first two books in this trilogy before reading this one, and actually got a little nervous about it while doing so. The first one was both better and worse than I remembered, and the second one suffers from the same thing almost every middle book/movie/story suffers from: not ending all the problems, and quite often leaving everyone in a bit of a lurch.
Thankfully, and awesomely, this book rose above the problems of its predecessors. The writing was a lot tighter, the characters did things that were not only actually in character (Clary dating Simon? Even for a little bit? Sorry, no.) but things I could actually get behind. I really appreciated that in the end it wasn't ONLY about the plucky young heroine saving the day, even though she played a pretty significant role.
All in all, I think this trilogy is probably my favorite so far of the fandom people publications, and I wouldn't hesitate to recommend it.