I've now finished the book.
At 87% through (sorry Kindle makes page number refs hard) - an explanation in the text altered my understanding of the Cainen aeon which is the birth-origin of the hero, so lets look at that first because the author's intent there shows up some wider issues.
The undying creatures of that aeon, whose world is a nightmare of perpetual immortal, rape, breeding, war etc - where the still living bodies of ones adversaries have to be buried so as to 'make room, make room' are the outcome both of eating the fruit of the tree of good and evil, and the fruit of the tree of life. I was wrong in my theory it was just the later.
Unfortunately while the description of the world is graphic and effective - I can't believe in it, either in or outside of a biblical perspective. [I could have believed in it if the entities had no intelligence, hence my theory, but with it I can't accept the premise that there is no possible gain from co-operation.]
Non-biblically, I'm unconvinced by the author's 'given' that there's no reason for co-operation among immortals, and hence never an end to the every being for itself melee.
An obvious good resulting from mutal co-operation for instance is *not being raped* the most logical result I think would happen from an immortal set up 'as given', would be armies of women co-operating to bury the (rapist) men, and an immortal lesbian sisterhood ruling. [I think it may be telling that immortal women have no 'agency' in the author's Cainan aeon.]
Another obvious good - where offspring are immortal competitiors for whom you feel no affection is, after several generations of working that out - is contraception.
Now Wright as a Catholic of course hates this and considers it sinful, but that's not going to dissuade a race of sinful immortals, whose alternative is continual attempted murder/ enforced perpetual solitary confinement. [It's not clear what happens to an immortal buried beyond the compression point of flesh, as their mass and structure doesn't obey conservation of mass laws, but being crushed under the earth forever isn't very nice either.]
In short, this bit of the book fails for me because the consequences of a set of given rules are what the author wants rather than what I think logically can be shown to evolve from the rules he has set in place. This impacts belief.
Biblically, my problem is - if you're writing a book that takes as its premise that the biblical account is at least mainly true (although the book doesn't imply a short geological age for the flood, nor explicitly does it have a worldwide flood- as it has chinese geomancers surviving it in their lands by deflecting it with dragon energies (reportedly)) - I think you have to cleave to the 'fundementalist'/biblical as much as possible, so when God drives Adam and Eve from the garden in Genesis and sets the angels with swords there to defend it (He only does this in one aeon incidently, ours) - he leaves a humanity which is - if not immortal - biblically very long lived. Long before it would fill the world sufficiently to approach the continuous warfare conditions of the Cainen aeon, it's discovered co-operation 'making nice things' (another obvious co-operative good, nice things > shelter and clothes) and set up the foundations of babel - so what stops that Cainen aeon running parallel to that only with immortals? [Co-operation being discovered long before the all vs all collapse point] Only so far as I can see authorial fiat.
This happens also as we head on, with the books' use of vampires (Those Who Quaff Blood Like Wine). Wright wants to set the rule that the cross works [automatically] as a dynamic symbol of christ's power not of the belief of the wielder - this is let me stress absolutely fine as a given in a vampire using novel, vampires are often glossed as having an origin in sin, and I can see why Wright doesn't want to go down the 'faith as energy' route [which for instance in Doctor Who sees vampires defeated by faith in the Russian Revolution, or the Doctor's faith in his companions] but there needs to be consistency both thematically for 'vampires are like demons' and for similar issues 'what you believe vs it's God's power/action' Wright's vampires however aren't vampires, they're people from an alchemic aeon who have replaced their blood in part with alchemic silver (?) and lost the part of the soul that makes moral judgements - this in itself is nice invention, but as a backstory, how does it justify the automatic curse of the cross upon them? Is alchemy or soul-lessness inherently cross invoking, if its not trad vampireism? We don't know. Equally in the final battle of the book, Foster Hidden who it is revealed is a worshipper of Odin invokes Odin, and is seemingly as a result empowered in combat. Is that his faith? Is that God choosing to empower a believer in a false god, because even though Odin is not a real God, the cause and the faith are good (but if so how is that not 'the faith' of the user). Or is it Odin, but if so what does this do for the 'biblically true' backstory. If X happens because God ? chooses that it should, how can you tell that your belief that God ? is God Y(the one you've been taught of) is true rather than God Z (Odin)? If a 'real' in the book God can empower an Odin worshipper, how do we know the only 'real' God in the book isn't Odin? 'empowering the Christ worshipper with the cross'. Once opened this can of worms wiggles both ways.
The first book ends in a rush of quasi-actions and quasi-moral questions that seem only partly thought through (or to be fair, perhaps only partly addressed in this volume - others may follow.) Is it always right to keep your word to monsters? Does it matter if you keep your word to one monster and thus be responsible for its killing if you do not defeat it, when your facing a Dark Tower filled with lots of monsters and there's a whole world of ones like the one you've made the promise too? [Does it particularly matter because you may have given that monster special superpowers when you got it to devour another different monster for you?]
And now we also come to two underlying threads/beliefs in the text which may make this a troubling book for many. One is Mr Wright's position on abortion - he's against it (which as a Catholic may be expected, and respected) but he seems to regard it as 'so obviously' the telling sin of our world that its practically our *multiversal identifier* "the world where they kill their children". Leaving aside whether or not there *are* sins, or whether this *is* one - while I would be willing to read a book in which the angels sorrowfully consider this our problem and/or the actual ethics of the position were addressed, the ball is startlingly fumbled by placing the criticism in the mouths of the masters and lackies of the Dark Tower. Reading a book in which our table manners are criticised by cannibals may be interesting and make a sly point - but it can also generate disbelief. I don't find it believable that (if abortion is evil as a given) it would not be used by the Dark Tower rulers to remove predicted malcontents [it could be argued that if they aren't allowed to be born the evil yet working astrology can't predict that they ought to be killed...but the evil yet working astrology has the rules the author sets for it, and it could as easily work from a moment of conception, which moment could itself be predicted when it resulted from lower nature.] What benefit do they have not to sin; would not the Evil Power pulling their strings want them to be Evil in that respect also?
The other thing is 'female agency' and 'depiction' - all the things done by woman to advance the plot (and being fair there are many) are off stage and rendered secondary by the decision to run a male main character as the sole narrator. The infatuation of the main character with the heroine isn't checked / amended by circumstances in the first book - I was rather hoping he might see a better prospect and companion and equal in the Monkey-masked thief, but as this book ends it is looking as if the infatuation is being foregrounded as the correct and obvious way to find a lover/mate/wife and indeed to interact with girls/women in general. I am not sure of this.
[A further aside, both Mr Wright and I have written novels with a Captain No-One in, why not buy my (and co-writer Jonathan Dennis novel) - see page aside! and compare the two. This is not a co-incidence as we both have Captain Nemo as a source!]
Final summary. As the first book in a series I mark this as 6/10. I'd probably read the next book, but I would be doing so in part in hope that some of my issues with arbetary worldbuilding in this would be addressed. I'd rate it historically as a good 'second' level SF/fantasy - Philip Jose Farmer's world of tiers, rather than his Riverworld. If it were Hugo nominated in 2016 on its own merits, I'd judge it against its peers but I would be surprised it had been considered Hugo level. As part of a slate I would probably No Award it.
[Tidied up a bit, clarificationary text in square brackets.]