Totally agree. The castle inhabitants have become more and more interesting Shaya, X'zaratl and Cliohna in particular and the way Rowan's relationship with them grows. Outside of it Delane and those in Rastedel are also interesting and I like Tarish. It's great it reminds me of Last Sovereign in that regard just gets you invested. I'd love to see more with Tarish actually she feels like someone that'd get on well with Rowan, they've both always been looked down upon in their societies but had the ability and subterfuge to rise to prominence but there's not much with her.
The twins are well written, it's funny just how much you want Rowan to turn the tables on them

. Though I suppose that could change in the second part if Rowan's relationship with one or both develops past antagonism.