- Alternate Character Interpretation: Nick. Is he a bumbling Smug Snake egoist who used Rachel solely to have an in to demons and magic, or does he only appear that way because it's all we can see from Rachel's narrative? There may be a lot more to Nick and his motives than the reader sees, because Rachel does not see every aspect of his life.
- Designated Villain: Lee and Piscary, though Lee seems to have retired from this role.
- Draco in Leather Pants: Kisten, Trent, and Nick.
- Piscary and other dead vampires could be considered an in-universe version of this as no matter what evil they preform their underlings will forgive them.
- Estrogen Brigade: Several characters have these most notably Trent and Kisten even after Kisten died.
- Evil Is Sexy: Al, Trent, most vampires.
- Fan-Preferred Couple: Several. Rachel/Ivy is the big favorite but Rachel/Kisten and Rachel/Trent are also common pairings. Less common but present are Rachel/Jenks and Rachel/Al pairings.
- Internet Backdraft: The revelation that 'Kim Harrison' is a pen name for Dawn Cook has created an odd amount of backlash among some fans on various forums. Whether or not this is large enough to create a Broken Base has yet to be seen
- Les Yay: Rachel/Ivy and Ivy/Skimmer Ivy with Rachel to the extent that some of the readership sees them having more chemistry than many of her male love interests.
- Magnificent Bastard: Al
- Meaningful Echo: In Million Dollar Baby, (told from Trent's POV), he briefly reminisces about one of his former horse whisperers, who talked too much, even in bed. Later, in The Undead Pool he tells Rachel that he hoped she wouldn't be a talker right before they sleep together for the first time. In that same scene in The Undead Pool, Rachel notes that it's the quiet ones you really have to watch out for, in this case referring to Trent.
- Moral Event Horizon: Many for the villains including Piscary's off-screen rape of Ivy and Lee allowing several innocent people to die in an explosion on his boat. For some fans Trent's murder of Brett also evokes this trope. Kisten originally setting the bomb on Lee's boat to begin with seems to have avoided this because to most fans Beauty Equals Goodness.
- As if we needed more proof that Ku'Sox is a complete bastard, in his latest exploits he kills an infant. Keep in mind, this infant would've even been useful to his plans at the moment since it had Rosewood Syndrome. He just did it to mess with Rachel cause she was rescuing the nursery of terminal babies he stole. Guess Kim needed to stress that yes, in a world of grey and grey morality he has absolutely no redeeming qualities.
- In the prequel book, The Turn, We find out that Trent's namesake father is responsible for the plague that kills most of humanity, all because he was jealous of another elf's work. His punishment? to live, create Brimstone, and marry the elf he was willing to destroy and allow the blame to be taken for the plague, all because she decided to sleep with him once, and he got her pregnant. It throws a lot of another character's actions into a different light come the regular series.
- Our Elves Are Different: An additional example, based on a comment Newt makes to Rachel that all elves are good in bed. Given that it's coming from Cloud Cuckoo Lander / Murder Makes You Crazy Newt, it may not be all that reliable.
- However, Rachel seems plenty happy with Trent in that sense and demons seem to enjoy having elven familiars.
- Squick: A few examples in the series including the fact werewolves are the result of demons in wolf form raping human women in the middle ages and Ivy's play by play of her own rape
- Al's insights into the jaded excess of demons is a generator of squicky concepts even though most of it is Off Stage Villainy.
- The HAPA-staged murder scenes and the Sick and Wrong witch hunter murders.
- The way master vampires breed generations of their "children" for their looks and susceptibility to manipulation. Piscary apparently started with Ivy's great-grandmother.
YMMV / The Hollows