The Shadowhunter’s Codex is a companion to the Shadowhunter Chronicles by Cassandra Clare and I read it months ago. Then I went on a break and never finished my review… Aaaanyway, the book doesn’t really have a plot like the other Shadowhunter books because it’s quite literally a fictional study guide. The Codex has information on anything mentioned in the Shadowhunter books, from laws, to history, to runes! It’s a must read for any massive Shadowhunter fan, but it’s not necessary  to understand the plot of the series. I wanted to read it because it’s mentioned in most of the books and I was just super interested!