(You should be warned that this will be a long review...and there will also be some spoilers for the third book and definitely some from the fist and second books too, which I won't warn you about. I'll try for the ones from this book though)

A net of shadows begins to tighten around the Shadowhunters of the London Institute. Mortmain plans to use his Infernal Devices, an army of pitiless automatons, to destroy the Shadowhunters. He needs only one last item to complete his plan: he needs Tessa Gray.
Charlotte Branwell, head of the London Institute, is desperate to find Mortmain before he strikes. But when Mortmain abducts Tessa, the boys who lay equal claim to her heart, Jem and Will, will do anything to save her. For though Tessa and Jem are now engaged, Will is as much in love with her as ever.
As those who love Tessa rally to rescue her from Mortmain’s clutches, Tessa realizes that the only person who can save her is herself. But can a single girl, even one who can command the power of angels, face down an entire army?
Danger and betrayal, secrets and enchantment, and the tangled threads of love and loss intertwine as the Shadowhunters are pushed to the very brink of destruction in the breathtaking conclusion to the Infernal Devices trilogy. (taken from Amazon)
Objectionable:Language was a 1, there are battles fought with demons and reanimated demons with automaton bodies, many injuries, mass murder briefly described, kidnapping. Will & Tessa have sex but the scene stops after they both agree it's what they want and some clothes have been removed while they were making out. (SPOILER:they get married later) Supernatural creatures, an angel trapped and drugs mentioned.
Thoughts:Wow. This is going to be hard. I mean the wow in two ways. A)Wow, this review is going to be hard to write without rambling and confusion...and getting everything out the way I want it to. And B)Wow this book was so amazing! I was dying for this book ever since I read the last word in Clockwork Prince. And I was in no way disappointed. I was scared to start this book and at the same time dying to know what would happen. But I didn't want something tragic to happen that I didn't like. I didn't want Tessa to necessarily end up with either guy because I wanted her to end up with both! And I didn't want anyone to die. Never ever are they allowed to die. Which brings me to the warning to all readers...I cried a lot in this book at several parts. Near the end and during the whole epilogue the most though. The epilogue is evil and right and so tragic and sad and right and perfect all put together. But first the thoughts that come before that...
Plot & Writing
The plot was killer. From the first pages to the last word it was thrilling. The first chapter really got it started with a bang and there weren't really any slow parts except (possibly) a few pages in the middle. I enjoyed every moment I was reading this book, whether I was crying or not :/ Everything was tied up really well. (REALLY REALLY BIG SPOILER) The whole thing with Tessa's angel being a real angel? I adored that! I adored how everything was stopped when it was unleashed and she saved them all by turning into the angel. It was just perfect. (DONE) The romance side of the plot was tied up just the way I wanted (kinda) and I was really happy with the ending of this series. I loved every minute I was reading. I know I already said that, but it's true. I can't help but think of this book and just smiling. So long as I don't think about the sad stuff. Which was done really well and tragically. Like really sad and beautiful and makes me want to go cry some more. More on that later. The writing was interesting and kept you interested and had this refined and Infernal Devices feel. Like it was just for this series. Possibly the characters or a certain way Clare wrote for the time period and all, but I felt it. It was a really nice style and just felt like the books. It's weird :P
Romance, Jem, and crying.
(This whole section is going to be a big spoiler probably. Just so you know :D)
Though your body is without soul.
Though your mind is without thought.
We know your story will be retold.
We know you valiantly fought.
And though this battle you've lost,
another you've won.
~To Jem
(I wrote that ^^ after he had "died"...kinda dorky I know :P)
It was so beautiful. Well obviously the book not me, I had snot and tears all over me and wadded up tissues. I cried for a while after finishing the epilogue too. When Jem said goodbye to Tessa and Will to be a Silent Brother completely. When the life of Will and then the loss of him was told. Jem's tears when he found out Tessa & Will's first child was named James. Tessa wanting to tell Will something and he was gone. How she always saw him as the young Shadowhunter she knew, even when he was old and gray. And how she forgot his exact eye color, the stunning blue. (No...I'm crying again *sniffs*) All that kept me crying and still is. It was perfect how it came out. After about a century Jem and Tessa finally are able to get together, a cure has finally be found. Even though he'll die like Will one day, she still chooses to be with him and she proposes on the bridge they walked on in Clockwork Angel. Cassandra Clare said in the sort of historical note that the idea bloomed on that bridge and it seemed fit to end it on the bridge. I was scared and I was kinda right. I cried and everything was tragic, sad, beautiful and so torturous but I wanted it to be. It was PERFECT. I couldn't have let the series end in any other way. I forced myself to finish the epilogue and get past Will's death. But I was loving the characters the whole way through despite the tears. It ended beautifully. I couldn't have picked one boy for Tessa to end up with. Even though I was Team Jem. I was also Team Will at the same time :/ But everything about the ending and how she and they got both of them was perfect. The torture and then perfectness of everything evening out was so great. Will and Jem loved Tessa so much, but would have stepped aside for each other. Because they were so alike and loved each other so much. And she saw that loved them both and agh...it's so beautiful. *breathes deeply* I think I'm okay now.
Overall
This book, this series...it's amazing. You should read it. It's clean apart from brief language, a couple of a bit steamy scenes and some violence. And the plot, the characters everything else is beautiful. Will will make you laugh. Jem will make you smile. The character you will simply fall in love with, head over heels. And for the bookworm nerds out there who love the classics will love how many quotes and references there are to several classics in pretty much all the books in this series. I would recommend to YA (14 I guess) girls and y'all must read this series. It's one of my favorite, favorite, favorites!
Quotes
"Will," She whispered again, drawing her arms about herself. She was sure it had been his voice she had heard calling her name. No one else's voice sounded like his. But it was ridiculous He was not here. He could not be. Perhaps, like Jane Eyre who had heard Rochester's voice calling for heron the moors, she was half-dreaming. ~Page 307
"Charlotte?"
"Yes?"
"Have you won the fight about what to call the child yet?"
Charlotte gave a startled laugh. It seemed odd to think about her child now, but then why not? In death, we are in life. It was something to think about that was not illness, or Tessa's disappearance, or Will's dangerous mission. "Not yet," she said. "Henry is still insisting on Buford." ~Page 293
Cover:It comes down to this and Clockwork Prince and I can't choose a favorite. I love them both. I love Tessa's dress, her angel there for everyone to see, the book and mystery as it glows...what could it be? And her hair is gorgeous. The background (the bridge, it's the bridge I can't breath it's the bridge!!) is beautiful and perfect too :D
Stars:There is no other number. Only 10 :D No seriously, five with all of my heart and many exclamation points next to it :D
Love, Sierra
P.S. Sorry if any part of that ^^ is confusing...I have so many feeling about this book, the main one being that it is awesome and everyone who likes this type of genre and such will love it.