The Shadowhunter's Codex isn't really new information, and any fans of the series will know the basic information from the series, but The Shadowhunter's Codex goes into more detail about everything about the Shadowhunter's world.
The graphic of the book in this post does not do it justice, the detail gone into the cover and the spine make it look like an actual copy of the codex, like it is an old book. When you open the pages you are not only greeted with more information, but also pictures about the items or creatures mentioned.
It also has annotations from Clary, Simon, and Jace sporadically written in the margins, at the end of paragraphs, or in sections meant for the Shadowhunter to answer questions, which end up being this trio writing and answering each others points or questions, with some hilarious one liners.
'Simon you don't have to make pretend fangs with your fingers. You have actual fangs.'
'........for you and your companions will be Hunters of the Shadows.' LIKE MASTERS OF THE UNIVERSE™Magnus also gets his own section regarding possible reasons why people become Shadowhunter's, which also made for a very entertaining list.
16. Large bearded man on flying motorcycle appeared to take you away to a Shadowhunter school. (Note: Presence of flying motorcycle suggests bearded man may be a vampire.)The Shadowhunter's Codex is full of more information and detail into how a Shadowhunter lives, weaponry they use, and more information about every creature they battle, and while I thought I knew a lot about the world Cassandra has made, I definitely learnt something new reading this book. The Shadowhunter's Codex is a great addition to any fan of this world and will sit proudly with the rest of the series on my shelves.