It was written by a Wiccan and it's pretty focused on the religious implications of the things the writer found out after arriving here. It explains that Jesus definitely exists (the writer has met him) and he doesn't claim to be omnipotent or older than humanity but the Harrowing of Hell does seem pretty well-corroborated.
So one of the first things I wondered was how I got here without being a Christian. The answer is, we don't know. The best guess anyone has for who goes here is that it's somehow related to your personality. It might also be related to participation in rituals intended to cleanse or sanctify. There's been a lot of ink spilled on this topic and we're barely less in the dark about it than people on Earth.
Well, I figured I'd make the best of it. I wasn't as wronged by Christianity as some, and I figured, hey, at least Jesus is trying to do something about all the hells, and they're not his fault to begin with, so if I have to spend the rest of eternity singing his praises I can at least be a little genuine about it. You might be thinking the same thing. And if you're happy about that, don't let me stop you. But before you invest in harp lessons, you should know something very important: Christianity isn't true. Oh, sure, Jesus exists. He even really died for us. But lots of people have died for me who don't own my soul. If it wouldn't make any sense to say it about a firefighter, it probably doesn't make any sense to say it about Jesus.
If you look at the claims in the Nicene creed, they're mostly wrong. We don't know if there's one God. We don't have any reason to think Jesus is his son. We know Jesus isn't older than all worlds and that they weren't made through him. Arguably, "ascending" is exactly the wrong metaphor to use to describe how we get here.
(But if you were looking forward to the harps, nine of the gospel ensembles in town include harpists.)
They explain that there are Christians here, but the denominations are divided up differently: there are several sects that think this isn't the real heaven and the local Jesus is an impostor; there's a sect descended from the Cathars but which believes in the physical incarnation of Jesus; there's a wildly popular adoptionist sect with what the author says is absolutely kooky theology (the details of which are not included); there are some of the sects from modern Earth; and, of course, there are a lot of Arians. But the author ended up joining a coven, of which there are actually several around (the book includes addresses for the websites for three of them). The city has a large Jewish population, largely Karaite but the author can also provide addresses for Orthodox and Reform synagogues. There are several pages dedicated to interesting things about local Islamic theology, which has diverged considerably from Earth's sects. Mohammad lives on this plane, although not in this city. But it gets weirder than that. There are Greek mystery cults and dozens of other pagan faiths - not revived or reconstructed, so, in some sense, more authentic than the Earth versions, but still very different from the historical versions from having spent so long changing and adapting to new circumstances. In some cases their gods turned out to be demons and in some of those cases they've schismed based on whether they believe their real gods are out there somewhere; in other cases they have no more evidence for their gods than they did back on Earth. There's been some very interesting drama from some of the older groups meeting their modern counterparts in the past few decades. When they even have modern counterparts, which some of them don't.
So what should you expect from Jesus? You don't even have to think about him if you don't want to. He's like a president except there aren't election ads: he won't necessarily notice you as an individual. And he's probably not reading your mind even when he is paying attention, he probably can't do that. In theory he's an absolute monarch; in practice he's kind of busy and not good at governance and areas elect leaders that answer to him when he bothers to have opinions. He does teach part-time at one of the universities (all his lectures are available online, along with the full text of all seventy-three of his books; the main benefit of enrolling in his classes is getting to talk to him during office hours).
The type of thing that Jesus is is... unclear. He says he's never actually met his father. It's possible he's the same kind of thing as the demons in some of the hells, or half that kind of thing, but it's just a guess. The theological implications are underwhelming, and more damning for Christianity than for most other religions. Don't expect the writer to convert any time soon.