My covenant with The Demon's Covenant

I’ve just finished The Demon’s Covenant by Sarah Rees Brennan, and I’m feeling a pain in my chest, almost as if the book has marked me with some sort of third-tier demon mark and now the book can possess me and control me whenever it likes. If you are not familiar with the Demon’s Lexicon trilogy, then what I just said probably sounds like nonsense to you. But if you are one of the initiated, then you know how devastating Rees Brennan’s combination of breathless action, simmering passion, and cutting wit can be.

Warning! Spoilers ahead if you have never read book 1, The Demon’s Lexicon.