Caith mac Sliabhin has been cursed by the Sidhe. He wanders the world an outcast, with his companion Dubhain, a pooka who appears sometimes as a dark-haired youth, sometimes as a black horse. In a valley where things are somehow terribly wrong, they meet a beautiful young couple who need their help...a couple who may not be what they seem.
Though set in a Celtic fantasy world reminiscent of The Dreamstone and The Tree of Swords and Jewels, this book is more like Cherryh's "human among the aliens" SF, such as Hunter of Worlds or Foreigner. The aliens, in this case, are the Sidhe. These aren't J.R.R. Tolkien's elves. They are like forces of nature, unmoved by, perhaps even unable to comprehend, the things that are important to mortals. Yet one gets the feeling that they are fond of Caith, in their inhuman way. Poor Caith.
Cherryh has a knack for hard-edged fantasy, and it's on fine display here. As in Rusalka, magic works in this universe according to rules and limitations that make it seem almost like science. The characters also have more of an edge than you commonly find in fantasy. Cherryh's characters are always interestingly flawed, but Caith and Dubhain are especially so. Caith has had an exceedingly rough life, and has good reason for carrying the chip on his shoulder he does. He's basically a decent guy, but his hot temper and stubbornness often get him into trouble. As for Dubhain...well, he's a dark Sidhe, a pooka whose job it is to take horse form, lure men onto his back, then drown them. Talk about having a dark side! Nevertheless, he has a sort of elemental innocence that makes it easy to forgive his mischief.
What Pat Nussman called "the magic circle" - a situation where a pair of characters are forced to rely on only each other for trust and friendship - is quite literal here. Caith has been damned by Faery, more because of the family he was born to than anything he did to deserve it. He avoids human company for fear of bringing his misfortune on others. Dubhain is similarly damned for the crime of doing a good deed. In a moment of weakness, he rescued Caith rather than drown him, and for this failure, he was bound to Caith by geas. They are each other's punishment...but also friends, as much as human and Sidhe can be. Dubhain is wicked and feckless and not entirely trustworthy, but humans need companionship, and he's all Caith has - the only being it's safe for him to be with. Dubhain is a loyal friend, as much as a dark Sidhe can be, but he's not human, and doesn't live by human rules. He can't give gifts without strings attached; every kindness must be balanced by a cruelty, however small. It's just his nature, and Caith understands this, even as he curses it. They are devoted to each other, but neither will ever admit it. They taunt and tease each other incessantly, using sarcastic terms of endearment more suitable for lovers than friends.
This book is a sequel to "The Brothers," a story from Cherryh's 1986 anthology, Visible Light. (The story can also be read in the omnibus The Collected Short Fiction of C.J. Cherryh.) However, the book stands alone. The key points from "The Brothers" are covered in Faery In Shadow, in flashback. (The events of Faery In Shadow occur five years after "The Brothers.")
Faery In Shadow is one of my favorite books of all time. If the Sequel Fay appeared and gave me one wish, this is the book I'd want a sequel to. Alas, barring such magical intervention, it's not likely. Faery In Shadow didn't get much notice when it was originally published. Cherryh says that her publisher thought it was too dark and depressing. Many reviews and readers have said the same. Part of the reason for this is that these days, people just expect fantasies to be fluffy. And part of it is that, like many Cherryh books, the ending of this one wasn't really meant to be "The End" but "To Be Continued." It becomes quite different when viewed in that light.
UPDATE: In 2009, CJ Cherryh self-published a re-write of "Faery In Shadow" under the title "Faery Moon." It's a $10 electronic download in multiple formats, including plain text, PDF, and Kindle. (Google it, and it should turn up.) Included is the prequel, "The Brothers," some new art, a glossary, and an explanation about why she felt the need to re-write the book and why it go so little promotion in the US.
I've read both versions multiple times, and they're not that different. She says she put more emphasis on the dialect, particularly the difference between Caith's relatively modern speech and Dubhain's much older language. However, I found the difference quite distinct in the earlier version, and didn't really notice the changes. The difference I did notice is that there's a bit more explanation of what's going on...in particular, that the crime that got Dubhain bound to Caith for punishment was doing a good deed, and that (in Caith's view, anyway) compassion is a sin for a dark Sidhe.
Should you buy "Faery Moon"? Yes, if you don't have a copy of either "The Brothers" or "Faery In Shadow" and want one, if you want Kindle versions of either of those stories, if you just want to support the author or self-publishing, or if you're a really hardcore fan of Caith and Dubhain. Otherwise, there's probably not enough new material to make it worth the price.