(I think 3.5 stars would be my preferred rating, if half-stars were allowed).
I read this book as someone with a PhD in (pure) mathematics, so I was not the intended audience for this book (i.e. a general non-mathematical audience), and it's therefore a bit hard for me to review it.
I accept that it's a very difficult job, trying to describe and explain pure mathematics ideas and research to a general audience - it's something I've really struggled with over the years. I think the author did quite a good job of this, although, again, it's hard for me to be the judge of that.
I found the book clearly written, error-free, and fairly engaging, although it did take me over a year from starting the book to finally finish, so I did tire of it at times. I particularly enjoyed the explanations of elementary proofs (i.e. the proofs, and parts of proofs, that the author did give in detail) - I hope that a general audience was able to follow along.
Nevertheless, the book, and especially its conclusion, is kind of... underwhelming. Both the unfinished status of the ultimate problem in the book (the twin primes conjecture), but also because the actual detail of the mathematics that has got us to the current partial result, is nevertheless basically impenetrable for all but the total experts. But hey, that's generally the nature of pure mathematics. Maybe I'm just not cut out for it...
I saw Vicky Neale speak once, I think it was in 2017 at the Young Researchers in Mathematics conference at the University of Kent in Canterbury. The same year that this book was published. I think I remember being quite impressed by her, and the talk that she gave. I was very sad to learn that she died in 2023, at only 39 years old.
Being familiar with Vicky's voice meant that, in my head, she was narrating the book in my head as I read along. I generally quite like it when that happens, including in this case.
Thank you Vicky.