In true Clare fashion, it's not long before things start heating up so I found the pacing to be decent. I did find the side-plots were too numerous, and added to the length without truly adding to the plot. For example, Maia/Jordan's PoVs - while I really enjoyed seeing their relationship begin to re-build itself, I found it completely unnecessary to the advancement of the plot. All of their scenes could have been cut, and I wouldn't be missing anything related to Jace's disappearance/subsequent alliance with Sebastian and the plan to separate the bond between the two. It made for a lot of dialogue and very little action, which had me struggling not to skim while I read.
As always, every scene featuring Clary and Jace was overflowing with sexual tension and filled with uncertainty - was Jace happier now that he was bound to Sebastian, and if so, should she even try to separate them? If it's what Jace wants (when he's lucid), but it will ultimately cause his death, should she go against his wishes, to keep him alive? What is she willing to sacrifice - who is she willing to walk away from - if it means keeping Jace alive, even if it's a mere shadow of his former self? Would Jace even want to be with her once he realized what she had to do in order to save him? It got to be quite tedious, as I'm beginning to tire of the amount of ridiculous obstacles they have to overcome just to be together. I'm beginning to wonder if they wouldn't be better off separated, if being together is always going to be this complicated.
I did enjoy that we finally got to see Clary and Jace being more intimate - even if they left many steamier moments unfinished - as it was a nice reminder that Jace does actually care for her, even if he's not always the best at showing it. That being said though, I began to dislike many of their scenes because they seemed to only focus on Jace's looks! I get it; he's part angel (and has been since City of Bones), so he's got lots going for him. I don't need it shoved down my throat at every turn.
I absolutely despised Alec, and actually dreaded any chapter that started in his PoV. His insecurities were quite prominent in City of Fallen Angels, but they have taken center stage in City of Lost Souls. Everything that Magnus says or does is questioned, as Alec can't seem to understand that someone who has lived for hundreds of years might have had other relationships. I was distracted from enjoying even their more tender or romantic moments because of Alec's wandering thoughts about why Magnus hasn't told him everything about his past. I thought that his solution - turning to Camille for advice about his love life - was absolutely ridiculous; why would he trust anything she has to say?! She's been caught in a lie or in pursuing her own interests, in several other occasions - what's to stop her from doing the same now? And the fact that he even had to think about her proposal had me wanting to rip him from the pages and shake some sense into his head - in the end, he deserved everything that happened to him.
The one thing I did really like in City of Lost Souls was Sebastian. He was written so cunningly, that I was confused for most of the book about how to feel about him. I was apprehensive at first, certain that he was a monster without any redeeming qualities. But as I got to watch him interact with Jace and see him treat Clary with the care and concern one would expect of an older brother, I started to doubt my original feelings; maybe being bound to Jace had changed him, for the better. Part of me began to hope that Clary would be able to give him a second chance, and that his plan for the future of the Clave would be one worth investigating. It was Clare's ability to write someone as devious and evil as Sebastian that saved City of Lost Souls for me, as I was constantly battling myself over whether I felt he was truly changed or just playing on Clary's emotions.
Fans of the series will probably love City of Lost Souls. And like I said, as part of The Mortal Instrument series, I did enjoy it. But as the content becomes fluffier, as the dialogue becomes more forced, and as the plot becomes more outlandish, I find myself less enthusiastic with each new TMI release.