Favorable reviews of The Children of Men prompted me to read the source, a 1992 novel by P.D. James. The book deals with universal sterility in a near-future dystopia, but aside from this premise and the characters’ names, the movie would seem to have been substantially rewritten (based on the trailer – I haven’t seen the movie).
The Children of Men (the book) is a near cousin to Walter Miller’s 1959 A Canticle for Leibowitz. Both portray the persistence and decay of Christianity in a future where (to the narrator) religion is futile and true believers are opaque, offering no comfort. (Christianity buckling under futuristic social pressure has been a theme of science fiction at least as far back as the insane curate in The War of the Worlds.) Also like Canticle, The Children of Men features government-sponsored suicide amid societal collapse. There is an echo of Ender’s Game, too, in the central sibling dyad.
Canticle is more ambitious in scope and philosophy, and its “science fiction” setting is integral to the plot and action. The Children of Men, while a reasonable study of power and ambition, doesn’t make full use of its striking premise.