Monsters come in many forms, from the kind that have claws and fangs to those that look just like us; from the overtly supernatural, or unnatural, to those who carry their monstrosity on the inside, a darkness glimpsed only when it shows through the cracks.

My latest book, This Savage Song, looks at two kinds of monsters, the literal and the figurative, those who feed on flesh and blood and soul, and those who relish destruction, harm, feeding some dark passenger (as Dexter would put it) within them.

As much as I love the classic kind of monster, as a writer and a reader, I’m most fascinated by the monstrous (I even did my Masters in medieval depictions of monstrosity) incarnations of humanity, the darkness that lurks within. Here are five books that deal with monsters of a more subtle nature.

The John Cleaver Series by Dan Wells

This is a fun series to kick off the list, because it has both incarnations of monstrosity, from the demon John Cleaver hunts down in I Am Not a Serial Killer and those that populate the later books in the series, to his own monstrous alter ego, Mr. Monster. The literal monsters in this series embrace their darkness, while John fights to control his own. Cleaver is a sociopathic teenager working in his family’s morgue and trying not to become a serial killer as opportunity after opportunity presents itself. Instead, he tries to channel his dark urges into catching the murderers plaguing his town. To call him a hero would be a step too far, but his self-awareness and active decision to suppress his own monstrous urges is utterly compelling.

The Bill Hodges Trilogy by Stephen King

The monster in this series, Brady Hartfield, is entirely human (or at least he starts out that way). Brady is a disturbed young man who plows through a crowd at a job fair, gets away with it, and then, in classic serial killer form, gloats to the now-retired detective who failed to catch him. This cat and mouse game (beginning with Mr. Mercedes) has several strange and captivating twists, but Brady is the love-to-hate kind of monster, the one we long to see defeated. Brady’s fascination with suicide, and his mission to convince his victims to end their lives instead of doing it for them adds an even darker spin to the classic serial killer type, and the relish with which he does it renders him a truly monstrous character.

Illuminae by Amie Kaufman and Jay Kristoff

Illuminae is on the surface a space thriller, following two teens as they escape a planet, only to find themselves on a ship that’s being hunted down while a plague spreads among the crew. But the most captivating aspect by far isn’t the megacorporation trying to cover its tracks by destroying the vessel, or the plague on board. It’s AIDAN, a piece of AI that has developed a god complex. The most interesting monster at the heart of this space thriller is neither a human nor a supernatural entity, and Illuminae provides a fascinating look at the descent into madness from the perspective of machine instead of man, and the internal logic with which AIDAN justifies his terrible actions.

The Death and Life of Zebulon Finch by Dan Kraus

And now for something completely different, Zebulon Finch. The monster at the heart of this story isn’t really monstrous at all. But he’s not exactly human either. Zebulon is a teenage thug in the early 1900s who gets murdered, only to… come back. Uncertain of why or how he’s alive again, but trapped in a body that just won’t DIE (though it does take a beating over the century), Zebulon is on the ride (with us in the passenger seat) of a strange, dark, sometimes monstrous adventure through life, war, and immortality. He’s a thoroughly likable, if not entirely living, character, and the exception to my usual preference for very bad people. ;)

You by Caroline Kepnes

Speaking of very bad people, there’s Joe. The narrator at the heart of Kepnes’ extremely disturbing tale of obsession is one of my favorites, because of his moments of relative likeability. Unlike King’s Brady Hartsfield, there’s an undeniable (and thus extremely disturbing) likeability to Kepnes’s lead character. He’s a horrible person, stalking Gwinevere, slowly insinuating himself into her life, doing away with each and every obstacle, from friends to lovers, with ruthless precision and unnerving levity. We don’t want him to succeed, and yet, there’s an undeniable charisma to his character, a jocular amusement. We are so close to his thoughts that we can see the derangement, and yet, we can also see why, to him, his actions are rational. Where John Cleaver’s sociopathy is purposefully distancing, Joe’s ability to justify each and every thing he does makes him dangerously familiar.

Victoria Schwab is the author of The Archived and The Unbound, as well as the acclaimed adult fantasy novels A Darker Shade of Magic and Vicious. When she’s not haunting Paris streets or trudging up English hillsides, she lives in Nashville, Tennessee, and is usually tucked up in the corner of a coffee shop, dreaming up monsters. Her newest novel, This Savage Song, is available now from Greenwillow Books.