I really enjoyed reading this science fiction novel. It was a fun adventure with some clever ideas. I especially like the implication that sightings of cryptids (e.g. "Big Foot" and "Nessie") actually represent the temporary opening of a doorway between our world and the Earths of parallel universes where our species never evolved.

By far, the most notable feature of this book are the chapters which are presented as excerpts from a non-fictional book comparing the divergent evolutionary histories of the planet Earth in the different "branches" of the binary tree of possibilities. They are really interesting on their own, even separate from the characters and the story, and some of them seem to show a deep understanding of how evolution works. Oddly, two of the alternate evolutionary histories that are most important to the plot do not really make sense. Evolution of species is thought to depend on reproduction, mutation, and selection. If any of these features are missing, there is no reason to expect evolution (especially not the evolution of sentience) to take place. If this were a website about evolutionary theory, I would write a lot more about that here and discuss the question of whether the author was mistaken, just being intentionally silly, or attempting to make a deep point about the insufficiency of evolutionary theory to account for the evolution of intelligence.

However, this is a website about mathematics in fiction and I haven't mentioned anything about that yet.

One of the principal characters is a British mathematician named Kay Amal Khan who stumbled upon the existence of the multiverse accidentally by looking for a transform that would be useful in cryptography. Khan originally thought of it as a "purely theoretical extra-dimensional space" in which intercepted messages could be easily decrypted. Scientifically advanced Neanderthals from a parallel Earth explain that what she has really found are equations describing the branched structure of the multi-verse, and they solicit her help in saving all of the universes before they collapse into non-existence.

Unfortunately, other than making it quite clear that working with these equations is quite essential to the goal of saving the multi-verse, the book has very little to say about math. At one point Khan points out that the equations do not require the branching to always be binary, although it appears that the branching of the universes always has been. That is seen as a clue that the branching is not a natural phenomenon but rather an intentional act. I found that idea to be vaguely interesting, but IMHO all of the other references to math are too vague to be interesting.

Other characters often describe her work as "hard sums", which is rather unenlightening but understandable since Khan's work is supposed to be beyond them. But, even the quotes from Khan and the sections presented from Khan's point of view barely say anything about the math. For example:

Khan is once described as "an experimental mathematician" and later (in apparent contradiction) described as a "theoretical mathematician and physicist". All of this leads me to think that the author doesn't know much about mathematics, or at least hasn't put any thought into what sort of math Khan might actually be using.

Although there is not much interesting said about math in this work of mathematical fiction, the character of the mathematician is herself quite interesting. Kay Amal Khan is a foul-mouthed, extroverted, trans-female of Pakistani heritage and therefore unlike any other mathematician character in any of the works in this database (so far).