This is book 3 in the Mortal Instruments series. The plot culminates in Valentine's search for the third Mortal Instrument, the Mortal Mirror. Pretty early on, I figured out what the Mirror is. There was one character revelation that surprised me.
I like how Clare uses biblical references and winds them into the story. Since the Nephilim are part angel and are charged by heaven with ridding the earth from Demons, this makes perfect sense. In this book, we encounter two angels and they don't disappoint even though one is near death.
I am liking this series still. After a short break, I'll read Book 1 of the prequel series, The Infernal Devices. Book 2 of that series is set to publish in December of this year with Book 3 following a year later. Book 4 of Mortal Instruments is published but Book 5 is set to publish this next spring. Book 6 of Mortal Instruments is slated to publish Sep 2013. We'll see if I stay interested that long. I should know better than to start reading a series before it's completed.