I’ve now read the book, and the plot and characters are quite good. As expected! Buy the book!
There’s a somewhat confusing-to-reader backstory about the heroine being an early Christian heretic. She’s not really involved with Gnosticism. She’s involved with “gnosis,” knowledge, which is the old Alexandrian term for a form of mysticism involving the seeking of both theological and personal knowledge of Christ. (As seen in St. Clement of Alexandria and poor old Origen.) The bad body-hating, woman-hating Gnostics of Gnosticism took over the term, alas, and used it to mean esoteric and occult knowledge. (St. Clement, St. Irenaeus and other writers talk a bit about the distinction between gnosis and “so-called gnosis.” After that generation, Christians started to use other terms to avoid confusion.)
Chancy is basically playing around with this and with pagan Egyptian religion stuff, although honestly there seems to have been almost no overlap between pagan Egyptian practices and ancient Coptic/Orthodox/Catholic Christian practices. Alexandrian Christianity usually seems to have been dueling with Greco-Roman paganism, as in St. Clement of Alexandria’s apologetic work, Protrepticus. (Albeit I think it’s humorous as a fantasy trope to see literal “spoils of the Egyptians.”) There’s also a few twisting of bad Gnosticism stuff (reincarnation, bodies as not intrinsically connected to the person, secret passwords for traveling between levels of existence, blah blah) into Christian-acceptable stuff, as a theoretical reverse-engineering to a fantasy idea of gnosis “powers.” Since a lot of the false Gnosticism stuff probably was sucked in from a bad understanding of Egyptian religion or trendy Roman occultism (Irenaeus points out that there’s actually a Gnostic version of the Egyptian Ogdoad, albeit it’s a really tenuous connection!), this sorta fits with the fictional spoils of the Egyptians idea.
Spoils of the Egyptians aside, the entire “magic system” used by the protagonist appears to be more of a miracle system. She’s a saintly person who quotes the Bible; and then God grants her speaking of true things to have an effect, as a result of her gnosis of God. (Which is not the worst description, since it does seem to work that way for some miracleworking saints whose wills and love are pretty much at one with God’s will and love, which would indeed be true gnosis.)
Anyway, there’s not really much said about how exactly this character’s beliefs are heretical. Presumably it’s not something that comes up in routine conversation. Of course, neither do the considerable differences between Mormonism and Trinitarian Christianity, or the Arianism of Jehovah’s Witnesses.
(If you want to have fun with early Christians and magic, the Recognitions of St. Clement (ie, the future Pope Clement I of Rome) is a really fun early Christian “adventure novel” with all the typical Greco-Roman separated siblings, as well as Simon Magus doing wicked magic. There’s also a bit of travelogue to famous Roman sites that don’t exist anymore. Lots of homilies and religious debate as well, which is why Rufinus of Aquileia translated it from Greek into Latin. My other favorite is the book with the resurrected dried sardines and the talking dog. If you’re interested in early Christian mysticism, The Shepherd of Hermas is a good intro, and St. Clement of Alexandria’s Paedagogue and Stromata also talk a lot about it.)
To address another point of potential reader confusion, there is absolutely no way that you could confuse Purgatory with Hell. Purgatory is part of Heaven. That said, some European Purgatory literature does get rather enthusiastic about portraying poor souls suffering (unpleasantly though temporarily) in Purgatory (albeit to encourage the living to pray for the Poor Souls with no one to pray for them, and to mend their own ways). Still, I don’t recall anyone ever showing Purgatory having demons in it. Angels being stern is about as far as it goes.
In general, and as with Buffy, I don’t really think this “Hell” is actually Hell. If you wanted to argue that demons’ minions had settled some mundane-but-unpleasant planet in a weird dimension or plane, and then invited the demons to take over; and that this was where people were being “dragged to Hell” by evil wizards and demons – that would be a lot more consistent with orthodox Christian theology. But obviously every writer has the power to decree the rules of their own writing worlds, so I could be totally wrong on where Chancy is going with this.
As noted in my previous post, Chancy says that she wanted to write an urban fantasy where the heroine fought evil, and did not choose to go after the Sexier of Two Evils. The inclusion of a not-totally-bad demon (even if not as a love interest, thank goodness!) would seem to militate against this goal. But in a world where people are dragged to Hell unwillingly and in which demons can sire children a la Nephilim (as opposed to “the sons of God” being Seth’s descendants and “the daughters of earth” being Cain’s descendants), a not-totally-willing Nephilim could end up being dragged to Hell and putting on a front as being a demon. (Which I expect we will find out in some sequel.) Of course, a being which isn’t actually of the angelic kind (albeit partaking of some angelic powers) would not have an angelically unchangeable will, and therefore would be capable of changing his mind about working for the baddies. (And I suspect that’s where she’s going with this.)
I hope we get more books from Chancy soon, whether from this universe or others!
P.S. Bart Ehrman is not a good source for early Christian stuff. He’s the kind of guy who will say that a source [Epiphanius] is a big fat liar about heresies, claim that the source’s tale of being groomed for sexual abuse by the Borborites was obviously made up, and then will quote that same source as authoritative about the Borborites, without pointing out who the guy is that he’s quoting! Elaine Pagels is dippy and relentlessly misguided, but she’s honestly dippy.
Still, you’re a lot better off learning about early Christian writers from either the primary sources in translation (there are several good anthologies of excerpts, like Aquilina’s Fathers of the Church), or from standard works describing them like Quasten’s four volumes of Patrology. Rod Bennett’s The Four Witnesses is another good starting place.
If you want to know why folks like Ehrman and Pagels are so insistent about “other Christianities” being somehow better and different, you can blame a German scholar from the 1930’s.