Daniel Defoe Robinson Crusoe (1719)
Admittedly not science-fiction in the sense of Asimov's Foundation being science-fiction, but Jonathan Swift wrote Gulliver's Travels in response to Robinson Crusoe, and I'd call that science-fiction at least on account of the Laputan interlude. This being written at the beginning of the eighteenth century, back when those parts of the globe to which Crusoe travels were largely unexplored if not exactly undiscovered, this represents a journey into the unknown, or at least a journey into the poorly understood, and is therefore speculative fiction so far as I'm concerned, the Rendezvous with Rama of its day.
And of course it's widely regarded as a classic, arguably one of the first English novels by virtue of being a story which derives no inspiration from mythology, history, myth, or existing literature, and so it has a certain reputation. The opening chapters prove therefore surprisingly unappealing for something of such stature, these being an account of Crusoe's early life, the making of his fortune, his travels abroad, his lucrative trading of slaves, and all punctuated by the sort of whining and bleating of which only the pathologically religious are truly capable. Of course the point of all this is to provide contrast with Crusoe's subsequent marooning on an island of the West Indies, and a new life of relative hardship during which he becomes somewhat more appreciative of his blessings, and one fuck of a lot more readable.
Oddly, chapter after chapter of Crusoe discussing goat maintenance or how to build a stockade using only a pointed stick proves highly engaging, and I would imagine it is this central section which has granted the novel such staying power over the last few centuries. Sadly, it all goes a bit tits up once we meet Friday, Defoe's concept of those indigenous Caribbeans who survived the arrival of Colombus being typically eighteenth century. The notion that such people may not necessarily have been overly sophisticated seems fair, but the suggestion of their being savages, and cannibals in particular, is shaky to the extreme and tends to undermine the strength of the narrative. In The Man-Eating Myth: Anthropology and Anthropophagy (1979), William Arens sets out a convincing argument for cannibalism as anomalous in the great majority of cases, and a serious taboo in most human societies - either a rare ritual practice (performed for the very reason of its being a taboo, something which goes beyond the acceptable and therefore intrudes upon the sacred) or, more commonly, a derogatory label by which all those nignogs are defined as savage and therefore suitable for whatever treatment whitey may feel inclined to dispense in the name of either God or colonial interests. Whilst my bashing Robinson Crusoe in this context may seem like political correctness gone maaaaaaaaaad (etc. etc.), statistics fail to support cannibalism ever having been as widespread as Defoe and other eighteenth century types clearly believed.
Anthropology being a subject I've gone into at some depth, the latter chapters of Robinson Crusoe are rendered unfortunately implausible for me. Some have noted Crusoe's commendably enlightened view of his bloke scoffing neighbours: in a fit of cultural relativism he wonders what right he himself has to cast judgement upon such customs; but when the chips are down, he still behaves very much as one would expect, the white guy exerting his "natural authority" over those who have yet to discover Baby Jesus for themselves. This doesn't make him a terrible person, but it does mean that once he's done with learning how to tunnel out a cave using just a kumquat, he becomes predictable and sadly somewhat dull.
Robinson Crusoe is certainly readable, and is probably a classic by virtue of what it did and when, but it seems improper to excuse its being written in relatively unenlightened times when Gulliver's Travels, which came along only seven years later, pisses all over Defoe with about five hundred times the wit, and at least as much humanity.
This was written in December, 2011 by the way...