What is it with reinterpretations of judeo-christian religions in fantasy books recently? There's also been a certain amount of it, but it seems to be more common and more pronounced recently. Naomi Kritzer's series was very strongly into pseudo-judaism (well, i thought it was judaism, her sister said she thought it was catholic) and Kate Elliott's series is strongly into early catholicism.
But anyways, the other big feature of Crown of Stars is the relationship tangles. I remember some list talking about how triangles are insufficient for describing the relationship geometries in most anime, and it definitely applies to this too.
I'm going to try to map out the relationship web, just because it's so insane, anyone who hasn't read the books and/or doesn't like insanity will probably be bored :)
Liath is probably the main focus of the web.
She's currently in (mutual) love with Prince Sanglant. Originally she was in an abusive "you can sleep with me or you can go sleep in the barn in the middle of winter" type relationship with the priest Hugh when she went into bond slavery. Hugh wants her back, but in the meantime he seduced Princess Sapientia and got her pregnant. However now that Sapientia's proven her fertility she's going to marry some outkingdom prince. Liath's childhood friend Hanna is irrationally attracted to Hugh even though she knows he's a bastard. Princess Theophanu seemed to be interested in Hugh due to jealousy issues with her sister, but then she found out he's a bastard and has fallen in love with someone else.
Ivar, Hanna's foster-brother, was the first person to fall in love with Liath, and tried to help her escape from Hugh, for which he got sent off to a monastery to be a monk. He's still romantically/sexually obsessed with Liath, but has also developed a religious obsession with a royal named Tallia who was staying at the monastary and who was proclaiming a heresy. There's also a lot of tension going on between Ivar and another monk-in-training named Baldwin. Bladwin entered the monastery to avoid marriage to a duchess he didn't like, that duchess happening to be Hugh's mother. She tracked him down and demanded they turn him over, which they did, and sent Ivar along too because they'd found out about the heresy. Baldwin seemed like he might change his mind about the duchess after the wedding night, but he eventually decided to run off with Prince Ekkehard instead, and they took Ivar along too.
Alain has had things a lot simpler. He's almost had run-ins with two random girls, then was interested in Liath for a bit, then ended up marrying Tallia. (After she got kicked out of the monastery for the heresy thing and they thought marriage might "settle her down.") However Tallia wants to be a nun, and failing that, wants their marrage to be a "pure" one. ie no sex, which will make producing a heir to the county a bit difficult.
A couple other people have expressed interest in Liath, including two dukes and a king, but nothing has actually hapened with anyone else.
I think that's most of the relationships.
So to follow one of the relationship lines, (if we make one assumption about where one of the relationships is headed) Ivar is obsessed with his boyfriend's wife's son's ex-concubine.