Iron Flame is the sequel of Rebecca Yarros' romantasy, preceeded by Fourth Wing, featuring further development of the revolution and conflicts arising in Violet's interpersonal relationships.

First things first: I cannot stand the protagonist, Violet. I have not liked her in Fourth Wing, either. Violet portrays toxicity for me, something I can do well without. Even so, I was hoping for her to have some character development (that proves good character building) and am troubled to find that I cannot discern much of it here.
Her conflicts dragged to a point that I feel like her slow-paced inner work does not match the high-strung tension of a fast-paced plot

that only ever took a breather during smut scenes

. That is not to say that inner work should be quick: Her disagreements felt repetitive -

a point that Violet herself acknowledges

- and it took away from the quality of the rushed plot, instead adding value by pushing lacklustre character development. Also, I wish 

Xaden took back saying that Violet is a rational being - she is not.

For a novel focused on romance, I dare say that it was lacking heavily in the romance department. I can only hope for The Empyrean series to improve from now on.