From what I've seen of other reviews, I feel like I have some different opinions on Iron Flame to other readers. I actually thought the writing was improved since Fourth Wing which I found to be very juvenile. Yes there were some grammatical errors that I picked up on and it was too long with a lot of repetition and info-dumping, but this book just needed further editing which it didn't have the chance to have due to the fast turn around. But overall I did think this book was more interesting and I enjoyed the content more now that we are outside of Basgiath war collage. 
In terms of Violet I think she has matured in her personal development, although not in terms of the romance with Xaden. I thought the relationship took more of a back seat in this instalment, and when they were together, they were likely arguing. I wish I enjoyed their romance more but I don't think it's very successfully executed, especially with the jealous ex-girlfriend we are introduced to.
The ending was a shock, I didn't see that particular outcome being on the cards so I will probably continue on with this series as it ends on a cliffhanger. For me I enjoyed Iron Flame more than Fourth Wing, an unpopular opinion but I am hopeful for the series to get better with each book.
3 stars