This book's theme is very much similar to "The Children of Men" by P. D. James or more correctly it is the other way round as this book was published before "The Children of Men". I haven't read the latter though as there is a general consent out there that the movie for once was better than the book. And having watched the fantastic movie starring brilliant and underrated Clive Owen, I have no plans to read the novel by P. D. James.
Now coming back to this book's review, I could only say that it started off pretty well but kind of dipped in the middle when it became over-preachy and philosophical. But I have to admit that the characters are well developed for such a comparatively short novel. Aldiss relies excessively on human philosophy in the latter half of the novel which cripples the pace somewhat, but that doesn't make this a particularly bad experience.