The following tale is a fantasy, pure and simple. It is a flight of sheer imagination. It contains no hidden meanings and none should be read into it; none of the sociological, economic, political, religious, or racial "messages," with which far too many modern novels abound, are herein contained. The Coming of the Horseclans is, rather, intended for the enjoyment of any man or woman who has ever felt a twinge of that atavistic urge to draw a yard of sharp, flashing steel and with a wild war cry recklessly spur a vicious stallion against impossible odds.I find it difficult, reading those words now, not to feel an immediate liking for Adams. His philosophy of writing, as expressed in his introduction, is one that appeals very powerfully to me nowadays and is very much in line with the best adventure stories of any era.
If I must further categorize, I suppose this effort falls among the sci-fi/fantasy stories which are woven about a post-cataclysmic age, far in our future. In this case, the story is set in the twenty-seventh century. The world with which we are dealing is one still submerged in the barbarism into which it was plunged some six hundred years prior to the detailed events, following a succession of man-made and natural disasters which extirpated whole nations and races of mankind.
And The Coming of the Horseclans is a good adventure story. It tells the tale of Milo Morai, a mysterious wanderer who eventually comes to lead the nomadic Horseclans, who ride the "Sea of Grass" -- the Great Plains -- and view "Dirtmen," as they call farmers, with contempt. Like Fors, from Andre Norton's Starman's Son, some Horseclansmen possess telepathy, with which they are better able to control their steeds and the sabre-toothed cats some keep as pets and hunting animals. Fierce but honorable, the Horseclans are, in some respects, post-apocalyptic Cimmerians, and there's definitely something Howardian about Adams's writing, from the obvious relish with which he paints battle scenes to the ambivalence he has toward the boons of civilization.
Just as interesting, I think, is the post-apocalyptic North America Adams details. Its main cultures are the Horseclans, the Ganiks (cannibal hippies), the Ahrmenee (Armenians living in the Appalachians), Mehrikans (rather generic middle American descendants), and the villainous Ehleens (Greek invaders). As he suggests in his introduction, Adams isn't trying to present a "realistic" future history, just one that allowed him to tell a good adventure yarn, so the world of the novel must be judged on that basis. I think it succeeds admirably, much in the same way that Gamma World does. However, I'm sure some would disagree, finding both the world and its characters insufficiently multi-faceted for their tastes.
In the latter case, I am inclined to agree. Most of the novel's characters, even Milo Morai, veer toward the one-dimensional, or at least are less well-rounded than one might expect even of pulp fantasy characters. In part, I think that's by design. Adams is more interested in the world-changing nature of Milo's accession to the leadership of the Horseclans than in its actual effects on Milo as a character. This is perhaps inevitable given some of the revelations made about Milo and his place in history and it is to some extent rectified in later books in the series. But there's no denying that many of the characters in The Coming of the Horseclans are ciphers whose primary purpose is to move the plot along.
That said, I have a soft spot for the Horseclans series. Although it's never (so far as I know anyway) been listed as an influence on Gamma World, I've long associated these novels with the game. The main reason I do so is that the North America of Adams's tales may be built upon the ruins of our civilization, but it's still its own thing. That is, it doesn't wallow in the past; instead, that past simply provides the opportunity to re-order society and culture so as to create a post-apocalyptic Hyborian Age. That's how I view Gamma World too. Likewise, Adams doesn't shy away from a number of fantastical elements, one of which I can't help but think influenced a later popular film series, though I have no evidence to support this (and, no, I won't say which series, lest I give away a major plot point of this novel). So, if you're looking for a novel to loot for ideas to use in your post-apocalyptic campaign, you could do worse than to spend a few hours reading The Coming of the Horseclans or its sequels.