In this brilliant book by Stephen Baxter, immortality is tackled properly. It won't be long before ageing is cured, and yet so few books, even sci-fi, take longevity seriously. Baxter describes how the undying don't have art in their environment, one is appalled by even the greatest piece of art after long enough. True, even the best song can pall after you've listened to it often enough on Spotify. You don't have to be immortal to feel like that, I find anything that's repeated becomes an infuriating burden.

But this book is about more than the undying. Coalescences are a recurring theme. This is where humans take the same evolutionary route as ants and wasps etc. They have a single breeding queen, and all the others work for the hive, in the knowledge that the hive shares the same genes as them. Perhaps we can see this happening in our society. Eggs are routinely frozen, stored and implanted into other women, so matriarchs can have babies that are genetically theirs without having to bear them. Housing is controlled by the older generation, so they can persuade their daughters to look after their siblings instead of having children themselves.

If all suffering, pain and all wrongs are to be wiped away, then ultimately that means that humanity, life and so the universe itself must not exist. In other words a perfect world is a word where nothing exists. In the end the protagonist, Michael Poole has this question put to him and comes to the same conclusion as me, he opts for life and an imperfect world.