Many reviewers have said The Mortal Instruments was less than excellent (others saying it made no sense.) I, a loyal and devoted reader of Cassandra Clare's series, and three of my other TMI fan friends, say the movie was 'okay'.
The beginning started out much like the book, but as it went on it slowly deviated from the original story. I can definitely see where people say that they couldn't make sense of it. I suppose I could take or leave the movie all in all. If you've seen the movie tell me if you liked it in the comments and if you've read the book rant about what they didn't do right.