City of Glass is the third in a six book series called The Mortal Instruments by Cassandra Clare  It is considered a dark fantasy that is intended for young teen readers and those who are older.   Reading this book takes you away to world ‘other’ than earth that have created for non-humans and those than are not totally human.  It really makes you think about the possibility of worlds other than what we would imagine.  It definitely fits into the genre of fantasy,  The world of dark fantasy is one of all darkness in comparison to a series like Fablehaven where there it is not ‘dark’ in nature.

The two main characters are Jace and Clary.  Clary is a sixteen year old that finds out that she is not human.  She enters into a world of darkness with Jace.  Their relationship changes in this book.  They had thought they were brother and sister, but ultimately find out that they are not.  More importantly though, they are friends and peers.  One of my favorite quotes shows their relationship. 
“Not everything is about you,” Clary said furiously.
“Possibly, Jace said, “but you do have to admit that the majority of things are.”

Another one of my favorite quotes can be applied to our world as well as the world of the Shadowhunters, “People aren’t  born good or bad. Maybe they are born with tendencies either way, but it’s how you live your life that matters.”  You can choose to act on the anger you feel or on the joy you feel - that is your choice, 

I did not enjoy this book as nearly as much as the first two volumes of the series.  The action parts of the story seem to be bogged down with the annoying and ever changing relationship explanations and details into the history of the all the people and creatures involved.  I would have rather had a family tree type chart of the history and relationship of these creatures than the long involved stories of how they came to be here. I think the female author forgets that boys reading this book would rather read about action than about history,  If one of my friends asked me for a recommendation of this book or this series I would not suggest this work. 

Cassandra Clare is a pen name for the 42 year old author of these books.  She has also written three other fantasy series of books including: The Internal Devices; The Dark Artifices; and The Last Hours.  All three of the series have three books each and do have fairly good reviews.