** spoiler alert ** 
 "We are bound. Cut him and I bleed." 
 City of Lost Souls starts off mostly with the search for Jace. After the incident that happened at the rooftop, Jace and Sebastian are now bound together. Basically, they're stuck together, with Sebastian being the dominant one between them and Jace, the submissive one (who knew right?) 
 Sebastian, who we know as Jonathan Morgenstern aka Valentine's son, has taken after his father in being the villain of the story. Most of this was already established in City of Fallen Angels, but in the fifth book of the series, Cassandra Clare delves deeper into the reasons behind Sebastian's plot. 
 Not only does Clare give us an insight to Sebastian's loneliness and need for love (so much so that he has to bind himself to the one person he could probably consider as a brother, who also hates him), but she also carefully illustrates the differences between Sebastian and Valentine. I liked the scenes that involved Sebastian and Clary when he was trying to convince her to see his point of view. 
 In addition, the book sheds a little light on Simon's characterization and his adjustment to being a vampire (Daylighter, really). His mother has kicked him out of the house and has failed to accept his new nature. As a result, he feels cursed and also, unwanted. This slowly seeps into his relationship (or lack thereof) with Isabelle, which I mostly enjoyed. 
 Simon, who's usually vocal about what he feels (mostly through sarcasm) and how he feels, is unable to ask Isabelle what they exactly they are. Isabelle, who's used to the idea of having what she wants without asking, doesn't understand why she has to be the forthcoming one in their relationship. The whole dance and build up between the two of them is quite entertaining. 
 Two characters who also delve deeper into their relationship and the meaning of love and companionship are Alec and Magnus. Another couple, who I consider to be one of my favorites. Alec shows his insecure and jealous side in this installment. Their relationship suffers from a disease of nonverbal communication. Alec can't simply ask Magnus about his past (for a reason unbeknownst to me). He also can't tell Magnus how completely insecure he feels, and because Magnus is ignorant, Magnus can't reassure him just how in love he is with Alec. 
 Insecurity drives Alec to Camille Belcourt (an ex lover of Magnus) and his actions drive a wedge between the two. I liked this new plot-line, mainly because it's exploring their relationship. Even though they're together now, everything still isn't peachy. Alec's decisions in this book made me very angry, and I actually agreed with Magnus' decision at the end of it. But this small dent in their relationship will probably make it stronger when it has been pounded out. 
 While I liked Jordan and Maia, I felt that the characterization of their relationship was a bit lacking. It almost seemed too rushed, especially when Maia seemed to be having a hard time accepting what Jordan did to her. I understand that they kissed in the last book, and while I thought that she had gotten over Jordan's crimes against her, Clare opened up the case and almost seemed to fast-forward to the happy times between the two. While it's understandable that Maia quickly gave into their romance because of the feeling that perhaps the world might end so she might as well give in, it felt like Clare couldn't juggle that particular plot along with the other story-lines. 
 As for Jace and Clary, they were the same. I think Cassandra did a good job establishing that Jace being bound to Sebastian wasn't the same Jace we had come to love. Reading the scenes between Submissive Jace and Clary, you could tell something was off. However, I was annoyed by his usual arrogant self. It seemed to be dialed up a notch to the point in this book, that in some scenes, it became almost obnoxious. We get it, Jace, you love yourself. And yes, we do love it when you're arrogant but some scenes didn't quite require your arrogance. 
 Another thing that I noticed in particular was how Clary went on and on about how handsome Jace was. I think his handsomeness should have already been established in the last three books. And with Jace going on about his beauty and awesomeness (in addition to Simon mentioning it, too), I felt like we didn't need to be constantly reminded. 
 Also, I'm very curious about Brother Zachariah. Having read two books in The Infernal Devices, I'm wondering if he is Jem Carstairs, especially after that conversation he had with Clary. I truly can't wait to find out. 
 In conclusion, City of Lost Souls was very entertaining. I enjoyed it, as much as I usually do when reading Cassandra Clare's novels. And I loved the characters, the action and the romance scenes that were stashed in between. Will patiently wait for the sixth book.