Shadowhunters and Downworlders by Cassandra Clare

Valentine.” You can say that again, demon boy. Sebastian, like his father (or perhaps his demon blood donors), didn’t get a humor gene. He’s also pretty smart, so he isn’t particularly susceptible to Jace’s attempts to anger him with his usual displays of mocking arrogance. “Nothing, not a flicker of emotion, passed across Sebastian’s pale face,” as Jace tries every trick in his arsenal, to no avail. Sebastian is weak, Sebastian is crazy, Sebastian is on the wrong side of history…nothing moves his “brother” until Jace stumbles on the deepest wound of all, the one that even
he
can’t joke about, because he feels its bite so strongly himself. If Sebastian kills Jace unarmed and tied up, Valentine will be disappointed.
    In the first few books, whenever Jace is given the chance to kill Valentine, he can’t pull it off because he can’t divorce himself from his long-indoctrinated need to impress the man he knew as Michael Wayland, the man he thought of as his father. His hand trembles in Renwick’s in book one, and when he kills Agramon on the ship in book two, his first, terrible fear is that it really
was
Valentine all along. Valentine is Jace’s enemy; he abused Jace, “beat Jace bloody for the first ten years of his life” (as Sebastian says in
City of Lost Souls
), but he’s also the only father Jace ever knew. If there’s one quality that Valentine has in spades, it’s charisma. It’s how he was able to get all the members of the Circle to do such awful things for him to begin with. Jace guesses right that Sebastian, despite his sociopathy and demon blood, worships Valentine in the same way everyone else did. And what’s more, Jace understands that humor and sarcasm is not the way to convince Sebastian that he knows what he’s talking about.
    In the first book, Jace’s momentary alliance with Valentine at Renwick’s is humorless; in the second, his pretended defection when Valentine shows Jace his terrible plan is similarly earnest. Valentine’s hold on Jace lives beyond his sense of humor, so deeply embedded in his psyche that he knows that the humorless, psychopathic Sebastian feels it too. So when Jace convinces Sebastian to fight him fair and square, the way Valentine would want (the argument is debatable, but hey, it works), there’s no joking required, or even warranted. His connection to Valentine is one area of his life where jokes do not suffice.
    In
City of Fallen Angels
, Jace is resurrected and reassured of his place in the world—or, at least, that’s what he wants everyone to think. His cocky swagger and amused arrogance are on full display, but those close to him are no longer fooled. Clary, when confronted with Jace’s continued vulnerability, thinks: “Alec and Isabelle knew, from living with him and loving him, that underneath the protective armor of humor and pretended arrogance, the ragged shards of memory and childhood still tore at him. But she was the only one he said the words out loud to.”
    No matter how hard he might be working to exorcise Valentine’s twisted teachings, to Jace, emotions and connection are still a weakness, and humor is the way he tries to keep his distance from the things out there—demon or otherwise—that might hurt him.
    An argument with Simon and his new roommate, the werewolf Kyle/Jordan, has Jace back in fighting form: “So basically you’re threatening to turn me into something you can sprinkle on popcorn if I don’t do what you say?” Exasperated, Kyle asks Simon if Jace “always talk[s] like this.” The answer, to Simon’s chagrin, is yes.
    Later, as the demon Lilith’s possession takes hold, Jace loses even this facade of sarcasm. Clary thinks “it was hard to see him like this, all his usual burning energy gone, like witchlight suffocating under a covering of ash.” You can