Definitely not a game but not just a rulebook either.

It sets rules for you to follow and describes the obstacles you'll meet along the way.

Think of it as something like a tabletop game that hides "the field" or "the cards" from the player.

But while I said that it's "like a game" I'd never say that it IS a game.

It's not specific enough to be called that. It's vague, vague to a point where it's easy to get into an argument about rules of the game (if there was someone to argue with that is), and that's not a trait a game or a rule set can have (by their definition).

And yes, there is no character for you to play here. There's nothing here about generating one. Starting Height?, age?, gender?, physical build?, preferences? all in your head and all up to you. Do we have combat training? Are we better than average at pathfinding? Did we ever pull a plant out of the ground in our entire life? We don't know and the author doesn't seem to care. He does care about companions having those skills though, so get ready to feel like a mister average-nobody next to them.

The worst part is that all the vagueness spills into the game mechanics. For example, an effect that describes you and your companion(s) getting body swapped mentions that combat prowess transfers with the mind, but would become useless if body is too different. How different is too different? again we don't know, author never told us. Oh wait, he also never told us what's our body like at the outset. Nor did he tell us how much we can carry, even though he did tell us that carry capacity between us and our new bodies DO swap.

Then there's the whole "creative use and combination of artefacts" going as far as telling us that we are able to combine them to build new ones, but never quite explaining the details. We know there's a workshop that offers services that help with "more complex work" but what is and what isn't complex is once again not defined. Nor is our skill at craftsmanship, and our general "craftiness" but that's expected since we're not even a character. You get where we're going with all of this? Yup, it's GM territory in a single player "game".

CYOA stands for choose your own adventure. You don't get to choose here, you'll need to create here. The entire advenutre?, no. But large chunks of it? yes.

Oh and the others have mentioned this already, but DO be ready to keep your own "character sheet". An extensive one.

Funny thing though... the author said that the game is "complex". And that why it'll be difficult to automate. I have to disagree. It's not even nearly so "complex" as it is just plain blurry and amorphous, and THAT is what the main difficulty with automating it will be. Machine code doesn't accept imprecise instructions. And before you can explain to it how your crafting works you have to first KNOW how it works. Having nothing but vague descriptions of equally vague ideas only works for communication between two sentient beings.

If you're in this for a story, yet you're ok with your imagination taking most of the work, ON TOP of being your own GM AND setting your own rules in the freaking middle of a game, then you will probably enjoy this.

I came here expecting a game I could navigate. By around a 4th level of the abyss I dropped the idea of being able to treat this as a game. I simply didn't have enough faith left in the design ability of someone creating something this vague (instead of a proper rule set) being able to outweigh the bother of keeping my own humongous character sheet. And after I did that I almost immediately lost all interest in it.

Why? Because even though it failed to become a game it was clearly meant as that and nothing more - Sets of pictures and descriptions of enemies/relics/curses/foraging opportunities just don't mean jack to you while you're not trying to put them to good use. And to put them to good use you need a well defined situation.

CAN I combine those two artefacts? Is my originally burly dude still able to comfortably lob 20kilos around after taking 5 stages of gender reversal? And if he's uncomfortable just how uncomfortable is he? And how much is that supposed to affect travel time? Seeing how part of that travel time is resting while part is navigating and part is moving and we were given no clue as to how those parts relate. See what I mean? You'll have to guesstimate your own actions all the time.

Honestly, I think I could have had better time just imagining my own story from scratch, and that says a lot because I don't consider that to be a fun pastime.

Don't get me wrong though this isn't completely hopeless. If the author ever gets over the absurd idea of creating the first ever sandbox ruleset (which is about as viable as an immobile satellite or an intangible handle) and actually starts defining how this is played, this might become quite a work.

P.S. Two other minor issues. One, the "game" frequently makes blatantly obvious "GM corrections"  (like taking time to tell you that a bird is inedible or that you can use balloon here but can't climb) and that noticeably devalues the experience. And two, at times it's just plain trips over itself while trying to find the "realistic" excuse for enforcing rules. For example, it claims that humans have a "need for sleep" which somehow is separate from "body's natural resources" (in an attempt to explain why sleep effects don't affect travel time). Newsflash - we don't. Not gonna bore you with biology here, especially since I'm no expert, but sleep solves very specific needs, and it's only those needs that make us rest for 8+ hours a day in a state of practically complete inactivity, nothing else comes even close (for example, muscles rest much faster and don't require inactivity of most of the body). If you DO solve them with [insert magic here] then you don't need to rest so much for any other reason, and if your [insert magic here] didn't solve them then it could not have done jack to remove your "need" for sleep in the first place.

In case it wasn't immediately apparent (and going off some of the reviews, it wasn't.) This is literally just a cyoa in the format of an html file. Its not an actual "game" nor is it supposed to be, where some people got that idea i do not know.

As for an actual review since i might as well do one since i am writing this after all. Its a very involved cyoa, originally based off of Made in Abyss where you can acquire magical relics of various kinds but need to take various kinds of transformations and or mental effects in order to get said relics. Food and water as well as travel time is also a thing. Theres *a lot* of stuff in it but similar to its psuedo-source material it can get pretty dark rather fast and has scaling difficulty so keep that in mind if you do want to go the whole nine yards and actually play the cyoa how its intended instead of just looking at all the content in without actually doing anything. 

Either way, whether you do an actual playthrough or not theres a lot of stuff to see and most of it is pretty interesting or nice to look at. Or existentially concerning. So if you like CYOA's that go beyond the generic style of nsfw ones then i'd recommend it. 

Really looking forward to more, a few things weren't totally clear to me though, like if its possible to forage for food while travelling between layers

First to clear up any misunderstandings it is a CYOA game, similar to games like Fame and Fortune on here, or a more mainstream game might be like thousand year old vampire. It is not a rule book, and it is infact meant to be played by indvidual players. In the current version you need to keep track of character by writing down your stats and gear and what not, so it is very pen and paper style.

It is very much a game about mangaging resources and mangaging your transformations. Your character is guaranteed to changed as they explore the abyss and surviving and having a 'good' ending can actually be very challenging if you also try to go deep int othe abyss. Having some imgination will make the game more fun but there is lots of pictures and stuff to get your imagination going. There are a ton of transformations into it and it is a pretty fun game.

First off I just want to say listen to Workthrower.  You this is absolutely 100% a rulebook the creators description is VERY misleading. there is no playable character.  and this is not what I was expecting.  Sorry not a fan of this game.  Love the concept and maze/dungeon games are my favorite but this is not even a game its a rulebook.  Which the author should just straight up say "THIS IS A RULEBOOK" in big bold letter at the top.  Very misleading