A very strong 4 stars here. Tchaikovsky delivers yet again.
His familiar mix of biological speculation meets an alternate-worlds plot grounded in the modern day. If I have a criticism of this book is that I felt the biological 'what-if' essays were a tad overlong and I found myself skimming them a bit.
That being said, there is a still a cracker of a book here. Strong, relatable characters and a plot that never quite ends up where you think it is going.
Recommended.