I wasn't super fond of that second trilogy, and to be quite honest I still vastly prefer The Infernal Devices. However, this last book did raise the bar a bit higher, and brought the series to an overall very satisfying end. 
 I do think however that Cassandra Clare needs a better editor XD There's a few heavy repetitions and awkward phrasing that could be heavily avoided. And someone needs to tell her to calm down on eye colours - yes, we get it, Jace's eyes are gold, Alec's are blue, no need to say it every single time plus it's not that big a plot point. 
 It's still nice and easily readable, and there are some really nice pieces here and there. The action is pretty well written overall. 
 I did like the plot, and the way new characters were introduced - which is makin me look forward to The Dark Artifices! And also how "older" ones were used. 
 A nice series overall, far from perfect but with good ideas and some good characters, and it's especially interesting as a gateway to its superior spin-off(s?).