City of Fallen Angels follows the story of Clary, Simon and their shadowhunter friends as they recover from the events that occured in Idris. Simon adjusts to his new Mark of Cain as well as juggling his vampire needs with his mortal life. Clary and Jace begin to find their feet after the death of Valentine and Sebastian.

Overall, I thought this story was more of a filler story. Its main focus is on the characters as they are brought back to reality and their lives in America. With the arrival of characters like Clarisse, this proves to be more difficult than it sounds. In comparison to the rest of the books in the series, I think this is quite boring. The only real action we receive in City of Fallen Angels is the last 2 or 3 chapters. In general, I found myself skipping pages and zoning out which isn't something you expect when reading a book in the middle of a fantasy series. I think this book is necessary to read if you want to continue with the series, but isn't the best book of The Mortal Instruments.