That's something interesting from Cassandra Clare. I quote it:
"Ever wondered about the enigmatic, mysterious warlock Magnus Bane? The only character to appear in every Shadowhunter book, Magnus has a past even more shrouded in mystery than his present. I’ve teamed up with acclaimed YA writers Maureen Johnson and Sarah Rees Brennan to create the Bane Chronicles, the backstory of Magnus told in ten linked stories."
That means ten great stories!
"Each story will be available as an ebook (Kindle, Nook, iTunes — however you usually buy ebooks!) on a monthly basis starting April 16 with the tale of What Really Happened In Peru. Each story will be released online for the next ten months — and then for those who don’t read e-books, the full print collection will be available in bookstores."
More info about this project, stories relese dates and synopsis (directly form Cassandra Clare) can be found on authors' tumblr webpage HERE.