'The Mortal Instruments: City of Ashes' Starting This Fall

We've already heard that Jess Postigo has written the screen play for City of Ashes. Now, Martin Moszkowicz informed us that The Mortal Instruments: City of Ashes will start filming in the fall. The director will still be Harald Zwart.

The Mortal Instruments - City of Ashes will go into production with Lily Collins, Jamie Campbell Bower directed by Harald Zwart.
— Martin Moszkowicz (@mmoszkowicz) May 8, 2013

Cassie mentioned in an interview a while back that they will film City of Ashes, City of Glass, City of Lost Souls, and City of Fallen Angels back-to-back. It's possible City of Glass could start sometime early next year.

What do you want to see from the book City of Ashes in the movie?