As it turns out, that story "Kazhe's Blade" that I liked from Sword and Sorceress XXI was an excerpt from the second book in this trilogy. "Trilogy" is a loose word here, because while all three books are about the same place, the first and second concern only slightly overlapping groups of characters. (The third brings the two together.)
Illumination is largely the story of Liath, an illuminator, whose powers fail her shortly after she successfully passes her trial. She heads off to see the Ennead, nine mages who loosely govern the land, in hopes that they can help her, but she's not the only person experiencing disaster. Blah blah blah, and she goes off on a quest.
This book has the not uncommon problem where the main character gets herself into trouble when she should have known better, although in this case Liath is a true idealist who simply can't bring herself to believe that people would be evil. Of course, Bad Things Happen.
While parts of the worldbuilding are very strong—the culture of the island is based on farmers, wrights, smiths, and other necessary laborers—the history behind it all is a bit fuzzy for my liking, in all three books. I'd like to see books about the world Eiden Myr exists in: what happened to it when all the magic effectively withdrew to a private island? Did they develop science and industry? Do they remember the mages? Or did the world plummet into a dark age and never recover, as is weakly implied?
The Binder's Road takes place six years after the events of Illumination, but doesn't mention Liath's name at all. (Liath is mentioned a few times, just not by name—I thought it was funny how the author did that...) Three sisters take center stage here, with powers stranger than magecraft: they can shape wood, hear ghosts, heal wounds with a touch, but as orphans they have to hide their powers from exploitation.
This book is of a similar style, but not a direct sequel to Illumination, which was disappointing until I got to like the new characters. I thought the ending should have been a chapter sooner than it was, but perhaps the author avoided that because that ending would only have been meaningful to people who had read the first book. (In the foreword for Triad, the third book, the author explains that she wanted readers to be able to pick up the story anywhere.)
Triad is the third book, and starts off with a bang: for three years, superior forces have been bombarding the island. (This is twelve years after the second book.) Their origin and motivation is unclear to the defenders, who are barely holding on, and have been exiled to the coast for their willingness to shed blood in order to defend others, a strange way to reward soldiers for sure.
Honestly, I was disappointed with much of the second half of this book: I didn't like where it was going. The tail end was good but the major decisions leading up to it I didn't like so much. Oh well.
The books have some sex,
Edited to add 7/27: Actually, the details of sex are easy to skip over (I added the strikethrough above on this edit), but it's impossible to pretend it doesn't happen. Magic is used for contraception, with the so-called "first freedom" applied to women when they reach sexual maturity, and homosexual and polygamous "pledges" (marriages) are, if not common, unavoidable in this story. One of my complaints about the worldbuilding is that, SPOILER, when magic is lost in events leading up to the second book, some of its artifacts are left behind (the triskeles marking trained mages) while some are swept away (the sterility spells on women). At the end of the first book, I was anticipating the threat of extinction due to an entire generation of sterile women, although that wouldn't really have happened since the existing children would eventually mature. End of added section.
Overall: pretty good soft fantasy*, but long (requires a significant time investment) and not really superb.
* Soft being somewhat derogative in that I don't think, even assuming that the magic described existed, a world could ever work the way it does in these books. That is, the society described here is not the logical result of the postulated world-structure, but instead a sort of feel-good utopia which has just incidentally been taken advantage of by evil people. You see the problem? Where do the evil people come from if their civilization is so great, and by the way completely sealed off from the outside world?