City of Lost Souls
This was absolutely my favorite of the series. The character development was so much better, and it was so much less predictable. It had a much darker feel to it than the previous books and it had a really interesting plot line. I still have problems with Jace and Clary as a couple and I think that there was a story line gone wrong with Magnus and Alec. I hope that in the sequel series they address Alec giving away his memory and then miraculously getting it back.