I picked this book up in a charity shop, having spotted the title and wondered if it was the same as the film. I’ve not read much PD James but I know her as a crime author and also as the author of Death Comes To Pemberley (which I do recommend if it sounds at all like the kind of thing you would enjoy).
The Children of Men by P D James has much more to it than the film that it inspired.
I am not even sure I can say “the film that was based on the book”. I spent the first half of the book wondering if the film was based on the second half, and the second half realising that even the denouement played out quite differently.
This is a very thoughtful book, with a wonderful examination of what it’s like to be in the middle of a slowly-happening gentle apocalypse. The world outside of Britain is not revealed to us but I suspect that it is rather unpleasant. Inside, things seem reasonably pleasant as long as you. Dystopia-implied or dystopia-light rather than a full-on disaster, but the clues are there if you look for them.