Summon the Keeper: Claire Hansen is a Keeper, a woman of magical Heroic Lineage who fixes the holes in the fabric of reality by using magic. She's accompanied by a Loyal Animal Companion / guard cat named Austin. She gets summoned to a Hell Hotel with a Hellgate in the basement and an evil Keeper immobilized in room six...and then the site babysitter/Dirty Old Man owner takes off and leaves her holding the bag. Unable to fix the stalemate situation, Claire realizes that she may be stuck running the hotel for life and waiting on the supernatural clientele that visit. Currently living in the hotel are a friendly French ghost named Jacques and the hunky jack-of-all-trades employee Dean. One's too young and the other's too dead, Claire says, but... And then there's her sister and fellow Keeper Diana, a girl who's not too uptight about making sure that situations don't explode.
The Second Summoning: Claire and Dean see if they can juggle a Keeper/Bystander relationship, but after they have Their First Time, all kinds of metaphysical consequences spring up. Specifically in the form of a teen angel and teen demon. Diana comes to the rescue in her own unique way, and gets a pet.
Long Hot Summoning: Diana's first summons after graduating from high school is to try and save a mall from becoming a portal to the Otherside. Claire joins her, along with Sam and a bunch of street kids turned elves. And she meets a girl. Meanwhile, Dean and Austin are at home dealing with troublesome guests.
The series ended due to Muse Existence Failure: the series was inspired by Huff's geriatric cat Austin, and after he died she couldn't bear to continue the series any more.These books provide examples of:
Adventurer Archaeologist: Lance is convinced that he's one. Dr. Redik thinks this is poppycock...but then again, he's the one sleeping with a mummy.
Always Lawful Good: Dean. He has one brief moment of hesitation about saving someone he thinks is abusing his girlfriend, and immediately thinks he should go to Hell for it. Later he actually kind of lies in order to keep Lance away from the paying customers.
Ambiguously Bi: Diana claims to be a lesbian but her one sexual encounter was with a man, then she meets Kris.
No Periods, Period, averted: Diana has to make multiple trips to a public restroom in order to close down a hole. Two teenage boys notice this and comment on it. Diana then claims to be menstruating and explains how that works in great gory detail. Then there's the time the evil overlord finds her tampon and she and Kris elaborate in gross detail as to what it's for.
Not Good with People: Claire. When Hell tells you, "YOU'RE NOT A PEOPLE PERSON, ARE YOU?", you know it's bad.
One Degree of Separation: Any time Dean talks to someone, they seem to have a connection to someone he knows from playing hockey.
Our Ghosts Are Different: Jacques can only manifest in rooms that hold an object that was in the room with him when he died. Keepers can also give ghosts flesh for a night, for sexual purposes. Jacques is all too aware of this fact.
Schoolgirl Lesbians: Zigzagged around. In the first book Diana claims that she is one and Claire's reaction is basically 'Since when?' Come the second book Sam takes advantage of his higher knowledge to reveal that her one limited sexual experience was with a guy and 'it wasn't his fault that it turned out so badly.' Yet in the third book her attraction to Kris seems to be genuine (and reciprocated) but by this stage Diana is out of high school so doesn't quite fit the schoolgirl half of the equation.
What Measure Is a Non-Human?: the main debate of book 2. Diana thinks that killing/releasing Samuel and Byleth is wrong now that they've become human and have personalities. Claire thinks that a demon needs to get eliminated from the world, period, and if the angel has to go in order to do it, then that's the case.