Sort of rushing this review, but this is the book I was hoping Cast in Flame would be.
From a narrative perspective, I think the pacing of Cast in Oblivion is the best out of the series. There is a LOT less exposition. It's almost as if you can sense where Sagara - or her editors - crossed out what swaths of what would have been a long, meandering rehash of Kaylin's internal monologue (or other character soliloquies). It's refreshing and I am glad that Sagara has realized that this is the ELEVENTH book in this series and that a tiny minority of readers would (mistakenly) be starting here.
There is also quite a bit of action in this book. I was afraid we would be stuck at an interminable dinner with the Consort the entire book, but this is concluded at about 50% (Kindle) of the book before the cohort head for the High Halls. I found what IS contained in this first half interesting. Barrani lineage and the reasons for Nightshade being made Outcaste are things that are discussed more explicitly, for example. Sedaris/her family/issues of succession are one of the major sources of conflict in CiO, and we have violent encounters with family retainers, lackeys, etc throughout the book as well.
The biggest conflict, of course, is against the shadow living under the High Halls as the cohort takes the Test of Name. Note: another review here mentioned the narrative inconsistencies vis-a-vis what the Cohort does or does not know about the Test of Name. That reviewer, I believe, is correct. However, this did not materially affect my enjoyment of the book.
Outside the Test of Name itself, the conflict is threefold: against the enemies of the cohort (and to an extent, the High Lord and the Consort); the shadow and, to an extent, Ravellon; and then the High Halls itself, which, like many of the buildings in the series, has a type of sentience.
The resolution of issues facing the latter (the High Halls) by Kaylin herself was mildly anticlimatic, 1) because I found it an unwelcome return to lengthy, self-indulgent pages devoted to Kaylin's "truth," self-loathing, and feelings of inadequacy. I get why it's necessary (she's a story-teller, she can only operate with Truths in these spaces, etc), but I skipped most of it and I'm not sorry. I've heard it for 11 books. Kaylin needs to go to a therapist IN BETWEEN BOOKS, THANKS, and work on her issues; and 2) because we're dealing, in part, with the healing or re-writing of the True Words at the heart of buildings and this is a plot that's pretty well-worn (Tara, Hallione(s), Helen, etc). I don't want to say too much about the battle against the shadow itself, also resolved by Kaylin (and Terrano), because I want to go back to reread these sections.
Another major positive step is that we're finally see some personal growth from Kaylin. She's proactively exploring her powers instead of lighting up like a Christmas tree on the fritz with no idea why whenever magic occurs in her presence. She proactively and consciously USES her powers in a semi-new way, which is even better. Kaylin also becomes more assertive (or competent) in her assessments of scenarios/risk and I'm happy that this is done without too much whining or complaining.
All in all, I'm pleased. If you've been hesitating because Cast in Flame was such a dud, I recommend buying it. Am planning to reread again quite soon to pick apart anything that I may have missed.