Thanks to my local library, I picked this up on a whim when I was collecting some other books - it's one of those books I thought I had read ages ago (since it was published in 2002) but on reading it, I found that I must have been confusing it with her other, older books like The Riddle-Master of Hed, which I definitely read as a teenager.
Anyway, Ombria in Shadow starts off like many other fantasy novels before it, with the death of a ruling prince and the unseemly jostling over who exactly is going to take over his throne. There is an heir, but young Kyel is still a child, there is also a grown-up bastard nephew who doesn't show the least interest in usurping Kyel, and finally there is Kyel's 'great aunt' who has been alive as long as anyone can remember and who has everybody running scared. Domina Pearl makes a bargain with the nephew, Ducon, that as long as he does not oppose her then she will keep Kyel alive and, seeing no better options on the table than this, Ducon reluctantly concedes.
Meanwhile, we discover that there is more to Ombria than originally meets the eye - the city has a shadow, a place that has always drawn Ducon for reasons he cannot explain, and within it a sorceress who has been helping Domina Pearl. Her servant, Mag, is trying to figure out who she is since she has been told that the sorceress made her out of wax when that patently isn't true. It's Mag's interest in first the prince's lover and then, curious to see if he's worth saving, Ducon that leads the various characters storylines to merge and bounce off one another.
So, for a book that seems like a generic fantasy, what makes it worth reading? Well, for starters there's the quality of the writing, especially when describing the other Ombria, which manages to be both beautiful and unsettling at the same time. And there's the characters, Ducon and Mag in particular, who are looking for answers all the way through the book and get them, only to be thwarted (as we discover in the final chapter) by the way that Ombria settles around them once more. Anyway, if you're looking for a good stand-alone fantasy book, I highly recommend this.