Now, that's impressive. It's been a long while since I last read Kay, and now I have a lot of catching up to do, since Lions of Al-Rassan was the best damn book I've read in a long time.
Kay's fantasy novels are magic-lite, and his countries are really just stand-ins for real times and places in history. In Al-Rassan, the allegory is thicker than usual even for Kay, with the titular country representing Spain under the Moors, with three religious groups standing in for Muslims, Christians, and Jews. I can't even say they're "thinly veiled" references, since they really aren't veiled at all.
The novel is set against the backdrop of an epic Holy War, but it isn't about the war. Instead it's about three charismatic characters whose lives and loves cross paths and intertwine. In any other fantasy novel, these would be the leaders and heroes who take the situation by the reigns and defeat some monolithic, evil horde, but in Kay's more honest depiction of a country at war there is no dividing line between good and evil, and it's the unstoppable force of history that sweeps the leaders along in its wake. At its heart, Lions of Al-Rassan is about people from different worlds who care for each other very deeply and how they are torn apart when those worlds come to blows.