The battle between Sebastian and Shadowhunters comes to a head in the last book of The Mortal Instruments series. Sebastian has taken the fight to a new level attacking institutes around the world and turning whomever he captures into the Endarkened. He wants the destruction of everything, but no one seems to understand that. Many of the Shadowhunters seem to believe that Sebastian is not truly a great threat. Clary, Jace, and Co. have no disillusions about Sebastian and if the Clave is not willing to take proper measures to fight Sebastian, then they will find their own way to defeat him even though it means putting themselves into certain danger. 
 At first look City of Heavenly Fire seems very daunting. It's a big book and covers a lot of ground, but I found that once you get into the story, it goes by really quickly. I often found myself stopping at certain points thinking how far the characters had come in the book from where it starts to the ending. 
 This is what everything in the series, starting with City of Bones, comes down to. Like most series there have been ups and downs, and I'm not strictly speaking about ups and downs for the characters (although yes, they've all had their fare share of tragedy and happiness). I'm talking about plot and storylines. There were moments in the series where I was positive I was not interested in going any farther, I just wanted to stop. But Cassandra Clare turned it around and I remembered what made me binge read the first three books in one weekend a few years ago. 
 Like many series endings, City of Heavenly Fire will not please everyone. As for myself, looking back there were a few things I didn't care for, but overall, I thought that Cassandra Clare did a fine job tying up this particular series. 
 First of all, I liked how settled Jace and Clary were with each other. They've already been through enough and we've had to read book after book filled with angst over their relationship. It was nice to see them work together as a team and as partners in Heavenly Fire because, let's face it, there's more important things going on what with Sebastian wanting total destruction of the world and all. Even the instances of uncertainty between Alec and Magnus and Izzy and Simon weren't as amplified as they have been in previous books and that's a good thing because, again see above comment. Plus, the characters (for all that they're still teenagers) are growing up. They've seen and experienced things many normal people don't, and it was nice that Clare acknowledged this in the writing of the characters. 
 Also, I liked the way the Cassandra Clare wove the prequel Infernal Devices into this series. It was very subtle. It started with Clary glimpsing Magnus talking to a girl at the end of City of Glass, and even though we didn't know it at the time it also involved a certain Silent Brother. This was done very well. If you've read The Infernal Devices, particularly Clockwork Princess, you know the end of that series / book delivers readers a rather nice surprise. Clare picks up that storyline and we retroactively get to see how it came about. Again, subtle. I didn't feel like it detracted from the main storyline. 
 What I was a little on the fence about was the clear introduction into Clare's next Shadowhunter adventure The Dark Artifices series (of which Lady Midnight is the first book). Clare takes a lot of page time to introduce us to Emma Carstairs and the Blackthorn children, specifically her best friend Julian Blackthorn. While their early introduction in the book justifiably ties them to the storyline of Sebastian in City of Heavenly Fire, the continuation of their storyline is nothing more than pulling readers into another series. Definitely takes away from the main purpose of City of Heavenly Fire. It kinda sorta felt, with the end of The Mortal Instruments so near, Cassandra Clare was "giving up" in places and filled it with enticement for her shiny new series. I almost would have rather the book been shorter and focused primarily on Clary, Jace, and the rest of the gang and the fight with the Endarkened and Sebastian. 
 That fight, however, was pretty predictable in my opinion. I think what was for surprising was the road to the inevitable fight with Sebastian. Clare threw in a few twists and turns that had me quickly turning the pages to find out how it would all come together for the final showdown. 
 Considering the Nephilim world will continue in another series, there's a definite feeling of anticipation at the end of Heavenly Fire. Of course, everyone comes out of the war scarred in some way, shape, or form and the anticipation of what comes next is high. Sebastian causes tension between the Nephilim and the Downworlders and the Accords that they've set in place, and to everything there is a consequence. 
 Because of this anticipation and the fact that there's already another series, it was difficult to feel the "final good-bye" at the end of Heavenly Fire. I would bet money this is not the last we'll hear of Jace, Clary, Alec, Mangus, Izzy, Simon, etc. I guess Clare's end goal was probably achieved because, after reading this, I will more than likely be compelled to read the Dark Artifices. What I do feel, though, is a slight sense of relief for our characters from the Mortal Instruments. Time to let them have a rest for a little while wherever it is characters go to rest when their story it told.