As Cassandra Clare gets ready for the release of her final Mortal Instruments, City of Heavenly Fire, she reflects of writing City of Fallen Angels and what it was like to realize she had more stories to tell in this world.

Much of the storyline in ‘City of Fallen Angels’ revolves around Simon and his growth into a vampire and his role in the Shadowhunter world. What was it like creating this new version of Simon? Was there anything that surprised you about character as you were writing? Is there anything that you would change?

I’m happy with Simon’s transformation as I wrote it. I was planning it for awhile, and it was one of my favorite subplots— an ordinary guy becomes anything but ordinary. Simon’s evolution throughout the books is dramatic. It isn’t just that he turns into a vampire, it’s that he really grows and matures through facing adversity. Being a vampire is part of that evolution, but it isn’t the whole thing. In some ways it was surprising to see Simon truly come into his own in City of Lost Souls. Those seeds were always in him, but in CoLS they come to their fruition in a big way.

This novel picks up where ‘City of Glass’ leave off but Clary and Jace are in a very different place by the end of ‘City of Fallen Angels.’ Did you always plan on the second set of books in the Mortal Instrument series? If so, was the plan for Clary and Jace to struggle to find their happiness?

TMI was originally going to be a trilogy. I had written a plot for a graphic novel about what would happen to Simon after the events of City of Glass, which is why I left so many threads untied at the end of CoG (where was Sebastian’s body, what would happen with Simon’s love life, the Seelie Queen’s threat, etc). When the graphic novel didn’t work out, I was left with this storyline and nothing to do with it — it wasn’t enough for a whole book on its own. However, while I was writing the first book in The Infernal Devices, Clockwork Angel, the way events played out in it gave me the idea for a new villain and conflict that might beset the cast of characters from The Mortal Instruments, and connect up to the plotline from the planned graphic novel.

I’ve always liked stories where the distant past comes forward to affect the future, so when I realized I could connect the events of Infernal Devices to the few loose ends left at the end of City of Glass, I realized I wouldn’t want to pass up writing that story, especially considering how much chaos I knew it would bring to the lives of Jace, Clary, Simon, Alec, Magnus, Isabelle and the rest! When I sat down to start writing the story of City of Fallen Angels, I had a detailed outline based in part on the graphic novel idea. But when it came to expanding the outline and writing the story, it just wasn’t working for me. I realized that the story I had thought I was telling was really a much bigger story — that my smaller, Simon-centric story had morphed into something much bigger, much more epic, and deeply involving the whole cast of characters from the first three Mortal Instruments books. I realized that what I had on my hands was not a single book that would wrap up the story begun in The Mortal Instruments, but rather the beginning of a new trilogy about these characters (The fun part was calling my agent and editor to explain “You know that one book I was going to write? Well, actually, it’s three books!”)

Was the plan to make Clary and Jace struggle? Well, it wouldn’t be a very exciting story if everything went their way, would it?

Jace’s character goes through a lot in this book. Did you ever find some of the scenes difficult to write or do you enjoy torturing your characters?

A little from column A, a little from column B. ; ) Sometimes I enjoy writing difficult scenes. Other times it’s just as bad for me as it is for readers, I suspect, but I am usually driven by a sense that it’s necessary.

Which scenes do you prefer writing more the make-out scenes or the action scenes? Is there a type of scene that is easier to write than another?

I like to write both! They’re quite different to write. I don’t have to ask my friends to act out the make-out scenes, much to their relief. I don’t find one easier than the other. It depends on the situation.

What has been the most rewarding part of writing The Mortal Instruments series?

Getting to share the story of these characters who’ve been living in my head for years. It’s been gratifying to see readers enjoy my books the way I have enjoyed favorite books in the past.

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