Note that the final chapter is especially disgusting and explicit, to the point it's arguably a better story if you end it on the preceding cliffhanger rather than subject yourself to the characters becoming vehicles for the author's thinly-veiled pedo-incest fetish. Great, thought-provoking SF apart from that (gigantic) flaw, though.
Yeah, I thought the main character was a little too insistent about... repopulating. On the other hand, if we're feeling generous we might say the author was intentionally confronting the reader with what is only implied by the Biblical counterpart.