Coturnix lays out his list of essential science fiction at Science and Politics. It's a very good list; go and see.
It was the listing of Kingsley's The Water-Babies (which isn't usually thought of as science fiction, but certainly qualifies) that started me thinking about Kingsley; hence the previous post. I'm a Newman man myself, but the Table of Brandon is nothing if not hospitably large, and there are interesting things in Kingsley. In my previous post on Ogilvie and early modern natural theology I should have mentioned Kingsley, because he is a representative of yet another twist on the relation of natural theology and evolution, as is easy enough to see in his essays, "How to Study Natural History" and "The Natural Theology of the Future," in his Scientific Essays and Lectures. Kingsley should certainly not be overlooked in such contexts.