After reading Throne of Glass I was fairly excited to read the next book as well and, between when it came out and when I read it, the author announced that while she had originally signed a three book deal for the series, it had been extended into a six book deal which was how she originally outlined it and that the series would completely finish. It seems as if she's already finished with the editing for Heir of Fire but I'm still happy since I do actually have a few YA series that are in unfinished limbo and have no desire to add to that list. Also, whatever my feelings on the individual books might be, I have to say that they have the best short, snappy but not one word, titles out there right now, they're rather fun to keep typing out!
Similarly to how I felt with the last book, while this book is certainly well-written it's failing to grab me the way my favorite books do and I'm not sure why. It might be because Calaena is still an enigma, while Maas clearly knows everything about her and is carefully dolling out the details. I haven't yet read the short stories, I was waiting for the new collection with the additional story to be released, so I am interested how much my opinion on her will change by the time I review Heir of Fire because of that and because her origins are finally revealed in the final pages of this book. On the one hand I'm a bit frustrated, it's such an overdone cliche and reminds of how glad I was when Lark by Sally Watson avoided this (and I was in middle school back then, I was already tired of this trope!) and don't see why CoM couldn't have handled it similarly. However, this reveal was well-foreshadowed so I had time to get used to the idea and wasn't quite as grumpy and this way we're certainly going to have even more dramatic and romantic tension down the line.
Speaking of which, we're stuck in a full-blown love triangle now and I am bored by it, especially since it seems like none of the characters know what they want and in my more cynical moments I'm convinced that all of them will end tragically as well. In the first novel this was balanced out by Calaena's strong, female, friendship but there was far less of that in this book and I hope that something similar returns for the next book, especially since at least some of the characters will be in a different setting (oh god please don't let that mean this is turning into a love polygon however). Which does bring me to my final thought, while I'm pleased that Maas now has a contract to finish her story the way she intends, how does she plan to fill up four more books? I think I see what Calaena's current plan is which would take more than one book but I can't see it taking four and I'm worried that the series might have an extreme case of "trilogy syndrome" and just bog down. I do think there's a secondary conflict they can switch over to if necessary (the story has brought up several times that most magic has vanished in a method that is itself magical and worrisome) but with this setting shift I can't see that coming up much in the next book at all. The series has a lot of plot lines but four books is a lot of space, and we won't even see how it plays out for several more years!