The 5th novel in The Invisible Library series by Genevieve Cogman, and the sequel to The Lost Plot.
Irene is a professional spy for The Library, an extradimensional and secretive organization that steals unique books from alternate Earths to bind them together and stabilize them, and which also works to maintain a balance of power between the Fae, schemers and plotters who thrive on Chaos, and the Dragons, schemers and plotters who thrive on Order.
She has been given possibly her most difficult and dangerous mission yet: Ensure that peace talks between the Fae and the Dragons, being facilitated by The Library, go off successfully despite the Dragons' main representative having been murdered. This means she must lead an investigation into the murder, with a joint investigative team including representatives from The Library, the Fae, the Dragons, and humanity, while of course forces unknown work to sabotage the peace conference and threaten the lives of Irene and her friends.
The Mortal Word is followed by The Secret Chapter.
The Mortal Word contains examples of the following tropes:
- Archetypal Character: The most powerful Fae are each an archetype unto themselves. The Princess, for example, represents the Princess Classic and all associated tropes, while the Cardinal is an embodiment of The Chessmaster.
- Blood Bath: The Blood Countess is known to enjoy bathing in the blood of her victims. Notably, the Blood Countess here is a powerful Fey who models herself after the stories surrounding the original Elizabeth Báthory.
- Both Order and Chaos are Dangerous: The nominative goal of the peace conference, and of the Library, is to stabilize the conflict between dragons (order) and Fae (chaos).
- Broken Pedestal: Irene’s interactions with Prutkov shake her faith in the Library’s infallibility.
- False Flag Operation: Virtually all the assassination attempts at the peace conference are a False Flag Operation in one way or another, but of particular note are Prutkov's blowing up of the Richelieu Library (the Librarians' portal between the world of the peace conference and the Library itself) and Ao Ji's murder of his own assistant Ren Shun.
- Family Honor: The concept of doing right by one's family is central to the dragons' hierarchy, though it is noted that the patriarchs and matriarchs of the great dragon families have a vested interest in maintaining this cultural norm.
- Gambit Pileup: Virtually everyone at the peace conference has some sort of hidden agenda.
- Genghis Gambit: Both the Cardinal and Prutkov try to pin everything on the Blood Countess to create a common foe for the peace treaty signatories. The former went as far as to invite the Blood Countess to the scene of the peace conference, while the latter simply took advantage of the situation.
- An Ice Person: Ao Ji commands the elemental power of ice.
- Ice King: Ao Ji is a rare male example, being as cold of a person and ruler as his powers imply.
- Idiosyncrazy: The more powerful a Fae becomes, the more compelled they are to follow their chosen archetype.
- I Do Not Drink Wine: Irene holds up a bottle of brandy to the Blood Countess, asking if she can offer her a drink. "I never drink... brandy," she replies, then complains "Dear me, how hard it is to avoid cliché!" She continues that she's certainly not going to accept any food or gifts that Irene offers her, this being because it would put her in her debt, something which Fae take very seriously.
- Incorruptible Pure Pureness: The Princess carries around a compelling aura of purity as part of her archetype.
- Inhumanly Beautiful Race: Dragons in human form always appear as exemplars of human beauty.
- Knight Templar: Ao Ji justifies his opinions and harsh actions on the basis that civilization requires the order that the dragons maintain.
- More than Mind Control: The Fae have a "compulsion aura" that drags humans into their personal stories by implanting false feelings and emotions. In the worst of cases, a Fae may entirely overwrite a person's personality with one more fitting for their narrative role.
- Order Versus Chaos: The conflict between dragons and Fae boils down to this, with dragons being the embodiment of order and the Fae being the embodiment of chaos.
- Never the Obvious Suspect: Zig-zagged. It turns out virtually everyone has attempted to sabotage the peace negotiations in some fashion.
- Not Me This Time: While the Blood Countess is responsible for the attempted bombing of the peace summit, she claims innocence over the murder of Ren Shun. In fact, she's rather offended that she's been falsely accused of this specific murder even though she already has uncountable gruesome deaths to her name.
- Peace Conference: The plot of The Mortal Word centers around a peace conference between the dragons and the Fae.
- Perpetually Protean: The stronger a Fae is, the less fixed their appearance is. The most archetypal Fae constantly shift between different versions of the Archetypal Character they represent.
- Reconcile the Bitter Foes: The Library seeks to end the Forever War between dragons and the Fae with the peace conference.
- Sadistic Choice: The Blood Countess tries to make Irene choose two of her friends to leave with, leaving the other two to the Blood Countess' nonexistent mercy.
- Screw the Rules, I Have Supernatural Powers!: When Ao Ji is exposed for the murder of Ren Shun, he opts to wipe out all the evidence and witnesses by summoning a city-destroying blizzard instead of going quietly with his dragon escorts.
- Treacherous Advisor: Defied. Irene grows wary of Prutkov only a little bit into her first conversation alone with him, where he declares his intent to make the Library indispensable to the dragons and Fae by any means necessary.
- With Due Respect: Irene uses it with Duan Zheng, the narration notes it as being "the traditional signal that one is about to be very disrespectful."
