Rather more than it seems at first glance (also, bias is fun!)
As one of the authors involved in the expanded 'verse I am naturally going to be biased, but to mitigate that I'm sticking to reviewing just Xenophila rather than any of the expanded works. I think that's safe. Human in Equestria stories, rightly or wrongly, have a reputation as wish fulfilment or plain and simple crap. The majority, in line with Sturgeon's law, are crap, or at least are mediocre. Most are some variant of Dude gets thrown into Equestria, saves the world, gets the Twilight and (if it's that sort of story) fucks everything in sight. Wish fulfilment at its finest. On the premise alone, Xenophilia appears to be just another one of those tales, a quick shag in the bushes dressed up as something else to pretend it's not "just porn". The premise is a little misleading, however; if anything, Xenophilia is anthropology porn (or hippology if you want to get picky). It expends approximately half its words describing the way this version of Equestria's culture functions in sometimes intimate (haha) detail, ranging over subjects as broad as mythology, history, cultural taboos, courting and - obviously, given the name - sexuality, seamlessly blending its various elements together into a highly entertaining erotic love story. Yes it contains sex scenes. Yes, when you boil it down, there is a hint of wish fulfilment present, but it never falls into that terrible trap of being grotesque and obvious about it. Every time something seems to be turning into just another bit of wankbait, the author introduces a new thread that makes the reader sit up and think for just a moment; not in a way that breaks the flow of the story, but in a way that enhances it. Conversations flow the way real conversations between lovers would, roving between topics as interest takes them. When the sex scenes appear, aren't forced and feel entirely organic, as if they're part of the whole instead of jammed in for the stimulation. The plot doesn't exist to justify the sex scenes (well, okay, it does, but only in the broad sense that it exists to exist), but rather the sex scenes actually drive the plot forward. And through it all, there's love. Before everything else, it's a romance. A romance in which a pony seduces a human and gets him into group sex in a crazy fantasy land. But a romance, nevertheless.