I so enjoyed the first book, even with its flaws. The second was a decent follow up, but the third book of the trilogy took a sharp nosedive in quality.
First and foremost, there were just too many characters. Killian, a major player in the first two books, barely does anything of note yet still manages to be a focus for the first 150 pages. Dyfrig, who was built up in the second book to be a major player in the politics of Blenhome, does practically nothing in the few segments that actually involve him. Madye and Rusgaan got more pages than he did, yet they were even less important. On the flipside, Deveron, the narrator/main character, had almost as much time focused on him as Dyfrig. Ullanoth likewise got no more than 10 pages, even though she's the one that brings about the end of the Conflict. To top it off, there were several named characters that saw even a paragraph, less space than some scenery descriptions, that felt like they should have a larger role, like Queen Risala. Beynor and Conrig were the only two characters that were both important and got decent coverage, but considering how flat they were (their plans and motives never changed across the entire trilogy) that's hardly a ringing endorsement.
Second, and this is true for all three books, a lot of the action scenes happen elsewhere. So instead of their being sections of fighting or adventuring, it's just a lot of talking and political/warfare counsels. This made the entire thing very dry, especially when there were terms used throughout the books yet no appendix/glossary defining these terms. Worse, unique/archaic terms were also used for distances and time, so it was hard to gauge just how threatening or dire certain things were because I couldn't fathom how far away or when they were happening.
Thirdly, there were a lot of elements that were glossed over or forgotten about. Ice-Maker was built up to be powerful, but was never used. The royal engagement went nowhere. The Didionites literally sat on their asses and died of heart attacks. What the hell were Cray and Thallasa doing besides just shuffling people around the island and why didn't they have a more active role? Why did Ullanoth not have a more active role? Why the hell did Beynor survive the poisoning?
Finally, the epilogue. Is that really the note things needed to end on? Especially how Wysganda, whose name appeared once before and was mentioned a grand total of three times in both the second and third books, basically took over Cathra. And Iduna, why does she not even warrant more than a sentence? Yes, she wasn't exactly a character (minor or major), but she still played a more significant role than Wysganda and Dyfrig.
Overall, I'd say that the first book is a good stand alone, but don't touch the second or third.