A woolly, wild space opera that boldly strides into high-octane multiverse space opera
When it comes to dealing with, and coming to terms with, books like Caspar Geon’s The Immeasurable Heaven, one has to immerse oneself in a text and a world that pushes the bounds of the comprehensible. I am going to discuss the book in those terms before trying to touch on anything else.
There is a theory of writing and reading genre fiction regarding how speculative a text can be before readers check out completely. You cannot, the theory says, provide too many shifts from reality before the average reader gets overloaded with the strangeness. Imaginations, in this theory, are not quite boundless. And I have found that I do love a sense of wonder in my SFF, and perhaps more than most, I have limits, too.
So where does The Immeasurable Heaven fit into this? Definitely into the deep end. Very much in the deep end.
We have big depths of time than the original series, with events that might, if I read the book right, take place in objective time over hundreds of millions of years in the baseline reality. We have vast numbers of solar systems in a distant galaxy in a far future where even supernovas have been engineered out of existence by a post-AI species that lives in stars, the Throlken. Oh, and the fabric of space itself is different now. The Throlken are basically the rulers of the galaxies, who live inside stars and enforce their laws remorselessly. They aren’t omnipotent or omniscient, although they are amazingly powerful. That’s a big enough canvas for most writers, but the author also makes this into a multiverse. For, you see, what I just described is the Surface, the base level of reality.¹ Below it are levels of reality called Phaslairs, created when choices are made and decisions split universes in a Everett-Wheeler-type formulation. These Phaslairs are always younger than the levels above. So the author provides us with a canvas not just of one large universe, but thousands of underlying levels of reality.
On this canvas with enormous potential, the story revolves around the Well, formerly known as the Inescapable Hole. While there are other ways to get down into the Phaslairs, the Well is a hole punched through realities and it’s the easiest way to head into universes below ours. These universes are younger, often very different, and while some of them are ruled, too, by the Throlken, some of them are “lawless” and most definitely are not. One other important thing to know about the Well and the Phaslairs is this: its a one-way trip in and down. Once you enter a younger universe deeper in, you can’t go back to an older upper one. Information, however, can and does pass up and down Phaslairs, but physical bodies and existences do not.
Or so it was thought.
The inciting incident for the book revolves around a Primal Scream that is captured by instruments at the Well. And, more importantly, the detection of someone, or something doing the impossible and ascending layers of reality. Who is it? What is it? And what are their intentions?
Three main characters are tied to this impossible event. Our major protagonist is Whira. Whira is an agent of Thelgald, an Alm (basically a monarch) under the aegis of the Throlken. Thelgald wants to know the provenance of the Scream, and so dispatches Whira on a very secret mission to the Well. (Thelgald is quite aware that the Throlken will not want them or any agent of theirs meddling and upsetting applecarts). Whira takes the slow path of traveling on a passenger ship, Gnumph, that really is a sentient, giant, spore-like creature that travelers live inside of, to head toward the Well and make a descent and investigate.
Our next point of view is Draebol. Draebol also works for Alm Thelgald, but has long since gone down into the Phaslairs. Draebol is a licensed surveyor/explorer/adventurer who lives down seventeen thousand levels of Phaslairs, busily sending data up and getting payments for it. So Draebol keeps on keeping on, creating a grand map of travels and adventures to eventually sell for a handsome profit. This relatively regular if exciting life is interrupted by a sudden rush of attacks and pursuits by various authorities. The knowledge that a seasoned surveyor has is very important when everyone is nervous about someone breaking the laws of reality...
Which brings us to our third major POV character: Yib’Wor. He was once a sorcerer king, and a tyrant at that, before the Throlken rose to power, so we are on the order of *hundreds of millions* of years. He was eventually overthrown and cast into the Inescapable Hole to fall forever. But he did not fall forever. And so he is the antagonist of the book, the one that demands action from everyone and everything else, as he slowly tries to climb back toward the Surface against all laws of reality. He is our inciter of the conflict. His is the only point of view that is in first person, and we really get into his head. I got a Miltonian Satan-like vibe from him (after all, consider the title, and consider the impossibility of climbing back up, that he is attempting to do).
There is a wealth of other worldbuilding details here. There are infraspheres, pocket dimensions for all sorts of sport and entertainment, including what is for all purposes a science fantasy MMORPG that can be accessed by beings across the galaxy and down into the Phaslairs, too. There is smart matter, strange tech and weaponry (including weaponry that can push you down a level of reality instead of hurting you), and much more.
There is one last bit of strangeness, which might be the part where the book teeters into the limits of what a reader can hold. And that is, none of these characters we meet are human, and most of them aren’t even bipedal with bilateral symmetry. And sometimes, going down into Phaslairs, one changes shape and form, too. So this book is populated entirely by creatures and sentients utterly alien.² The author makes it clear and impossible to miss that you aren't dealing with anyone or anything even vaguely human.
Put all this together, and add the author’s immersive and descriptive language, and I can’t help but wonder whether the book pushes that limit of how many dissociative genre elements a reader can reasonably hold in their head and still grok the book. I would never, ever, want to give this book to a new reader of science fiction. As it was, while I was reading it, I set aside the SF audiobook I was consuming at the time, because I did not want a gear clash in my brain between the far-future details and the kaleidoscopic worldbuilding of The Immeasurable Heaven.
Let me give you an extended quotation. This gives a sense of when the story decides to drop you headfirst into its world. Really, this is my final argument for the book. If you want to (or think you can handle) a text that is filled with passages like this, and the mental brainspace to keep the picture of it in your head, this book is for you.³
In the silt-suspended gloom something huge uncoiled. It scratched itself with a few lazy sweeps of its fins, scraping a peel of dead skin into the depths, before extending a tongue shaped like a fabulously intricate key and latching into the receiver. The apparatus glowed into life, startling a flitting ecosystem into the shadows and revealing the full, serpentine bulk of its user in a ghostly wash of light. The interior of the water-filled space lit up with every flicker and flash to reveal a cavern of gnarled, artificial stalactites and equipment that poked like instruments of torture into the creature’s lair.
The Translator, hundreds of meters from snout to tail, had never seen the galaxy with its own eyes, for it possessed none. It was likewise completely deaf, as most other species understood the term, relying instead on the single most sensitive organ for light-years around: a tongue equipped with twenty million pressure receptors per cubic centimetre, a tongue it had never seen.
Finally, the book is complete in one volume. We get a complete story here. (One thing that I appreciated, and in fact found necessary in the Amarathine Spectrum books was that in The Weight of the World and The Tropic of Eternity there were summaries of what had happened before. It would be triply necessary if this were the first in a series, but it is not.) It is a rich, complicated setting with non-human characters, and one of the widest canvases I’ve ever read in an SFF novel. As noted above, it’s not going to be for everyone, and not for readers who have not read science fiction before at all.⁴ The book teases that (if it does well in the eyes of the publisher, of course) the author could tell more stories in this vast universe. There are throwaway lines, references, allusions, and side notes that could be expanded into full novels. But there’s also ample space to tell entirely new stories.
Given the absolute trashfire that our world is lately, maybe you want an experience like few others, in a setting completely alien to our own. The Immeasurable Heaven is here for you. Coming out of this book is like emerging from a deep Phaslair into the Surface world, having experienced a realm (realms!) extraordinarily different from what you knew.
Highlights:
- Pushes the boundaries of comprehensibility in a SFF work. Requires careful attention due to overwhelming alienness and detail.
- Enormous canvas, one of the largest possible in science fiction—and makes very good use of it.
- Multiverse? Space opera? ¿Por qué no los dos?
- If you want to immersively escape the world, this book provides that in spades.
Reference: Geon, Caspar. The Immeasurable Heaven [Solaris, 2025].
¹ In theory, anyway. It is hypothesized that there are levels of reality, Phaslairs “above” the “Surface,” but that they are uninhabited by any life.
² The touchstone for this book, with its levels of reality, multiversal outlook, and the changing of bodies, is the recent Transmentation | Transience: Or, an Accession to the People’s Council for Nine Thousand Worlds by Darkly Lem. That book, too, with its enormous canvas and furious and fertile imagination, has a similar approach, where changing universes means changing bodies. That book mostly has its action on various planets or cities, although one universe has a long space-opera-verse chase scene involving spacecraft.
³ That makes me wonder and think. There are plenty of people who cannot visualize in their minds deeply. If I say “Picture an apple in your head,” some cannot see the apple, or see a very generic apple without detail, whereas there are people who can tell you what that apple smells and tastes like when you bite into it. I am moderately on that spectrum of sensory imagination, but know people who outrank me. Is this type of book harder for someone who is trying to handle all this detail? Or, conversely, are readers who can’t picture an apple the ones who would find the above easier, because they aren’t even trying to see the Translator’s lair?
⁴ I haven’t mentioned him to this point, but I think this is where Olaf Stapledon enters the chat, with vistas of time and space that this book dares to try. Stapledon’s is a much older and more compact style, and he would have told this story in a much shorter volume—but it would be just the ideas and not much of the meat. But that density of ideas and that vastness of time and space and willingness to really offer the reader that level of dissociation, that’s Stapledonian. This book follows proudly in that tradition even if its style is much more modern. But again: Stapledon is NOT for everyone. I daresay that if you don’t like Stapledon, this is not the book for you. The converse may also be true.
POSTED BY: Paul Weimer. Ubiquitous in Shadow, but I’m just this guy, you know? @princejvstin.