Science fiction has a tendency to ignore religion; this may have stemmed from its early Enlightenment-style emphasis on rationality, or it may have been sheer laziness, since predicting how some of our oldest cultural institutions would fare years into the (often dystopian) future is difficult at best.
There are notable exceptions to this, and the situation has gotten better as the years wind on and the genre refines itself. Writers aren’t always nice to religion, but they’ve generally stopped ignoring it as a force for (or resistance to) change. But even in scifi’s early days, there were some writers who not only included organized religion in their stories, but actually centered the plots on it. Most frequently cited is Miller’s A Canticle for Leibowitz. But just a scant year before Miller published his first and last novel, another titan of the early science fiction scene, James Blish, published A Case of Conscience, whose protagonist(?) is a Jesuit priest.
