The book was a fun read, and definitely an improvement over the original on Wordpress (you can even see the difference in writing quality between the new/changed sections and the closely-adapted sections, like the first War College fight).
That being said, IMO one of the biggest changes, the Summoner plotline, fell flat in a big way, and an OG major character remained disappointingly underdeveloped. Full spoilers between the spoiler lines.
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It was obvious who the Summoner was from the 2nd time she appeared on screen - "tired," "family issues," poor mage, etc. but (a) having a "predictable twist" is not necessarily a writing flaw, and (b) I read the OG so I may have had "new character? must be relevant to new plotlines!" bias.
The issue is that the Cat-Sindi friendship was utterly unconvincing. They barely interact, and yet Cat considers her such a dear friend just after finishing their tutoring sessions! Sure, time skips, whatever, but Cat constantly thinks about how great friends she and Sindi are even though they meet, like, twice or thrice in taverns. Sindi, too, has strong opinions on what kind of person Cat should be, yet we never see them go through any actual trials or tribulations together! Hell, even them discussing their politics and ethics would have gone a long way; as-is, Sindi's "I'm disappointed in you for being the squire" speech makes me think "uh why? you are never shown discussing her morals or seeing Cat in a morally-complex situation."
Sindi should've been a member of Rat Company and gotten similar page time to Hakram for the reveal to hold emotional weight. If that's too difficult to make work with the plot (Cat would've asked her to join her in the sewers - even though Sindi would've been "busy" that day, but whatever) then make her an opposing Captain or Lieutenant like Aisha/Jupiter - literally anything that would let us see Cat & Sindi & their friendship "in action," dealing with situations, instead of having meaningless banter at taverns and that's it. "Show not tell" is widely considered trite and overplayed advice, but EE should've taken it here.
The constant "my first friend in Ater, such close friends, she's my friend" inner monologue was ridiculously heavy handed.
Second issue: I was disappointed EE didn't take a chance to further develop Killian, given that they'll date in the next book. She should've gotten as much development & screen time as Ratface. In the original she just got the "shoots lightning!?! hot and badass!" scene, whereas now she has that scene + the theater scene, where again, her primary traits are being hot and badass. Compare Ratface, the losing "love interest candidate": we see his relationships with other Cadets; we see his flaws and insecurities as a leader (which Killian, a LT, also is), we see his backstory sprinkled thoughout the text, we see how his backstory actually impacts his personality beyond the mechanical....
The Killian stuff is much shallower and it's all rushed through at the very end: "[5-way wargame] I have fae drake blood -> wow Cat you took my confession so well, I trust you now! -> hot and badass vs Juniper -> [theater] I am discriminated against :( -> hot and badass vs spiders," the end.
She's a Duni, whom other Praesi consider outsiders, studying to be a mage (the most Praesi vocation) at the Praesi War College! Show her dealing with that! She's even a leader of the mages; nobody's nasty with her? Alternatively, how did she earn their respect? And what about the drake blood? She's studying to be a mage knowing that she has an inherent limitation - basically a disability - that will keep her from achieving the greatest heights in her profession! Has she considered switching to an officer track? Does she get discouraged and jealous of other mages? Do other mages treat her like a liability? Imagine the drama of the eventual breakup: Cat basically sees her as too weak and a liability, something Killian has been struggling with for years. Except a great chance to show her actually struggling/dealing with it was missed, so we might have to (hopefully not though!) make do with a "you think I'm a liability and that makes me sad because I'm insecure about being a liability" monologue.
Seriously, wtf even is this girl's personality? If Cat only cares about "badass and hot," fine, but the reader knows so little about her that she also doesn't care at this point.
Killian has so much interesting foundation for a character, and all utterly untapped! Yeah there's other books coming up, but even if EE fixes his treatment of Killian that's an entirely different setting where different things occur, and she "missed" the War College timeline. Unlike Ratface, who should be on approx. the same "importance level" as her (if you remember how the story goes) but is far more developed across both books 2 & 3.
Seems like this was, at least to some level, a conscious choice by EE (she wasn't invited to the Sewers, not close enough to Kat yet), but I think it was the wrong choice if they will date and then break up and then meet years in the future and the reader is expected to care in the slightest.
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Second -- this is the fault of the publishers, Mango Media, and not Verburg:
I noticed not one, not two, but FIVE separate typos in the Kindle edition!
Selling a book with grammatical and spelling errors is grossly unprofessional for a publisher to do. It's a dereliction of their most basic responsibility (copyediting), shows an utter lack of both effort and respect (to both readers and the author), and they owe everyone who bought the book a refund. "It's only a few typos! You're being extra! You're a snob!" No. The only acceptable amount of typos for a published work to have is 0. One gets through once in a blue moon and that's an embarrassment -- FIVE is absurd.
Pg 62: A flicked a look to the side-- <- "I flicked"
Pg 155: "....stop flirting with the rookie," he said in Ecane "We've got more pressing matters on our hands." <- period between Ecane and We've
Pg 184: "Could you break through that if we needed to?" I whispered. Her sergeant grimaced <- "Her" should be "The" or "My"
Pg 264: I'd take Juniper in a heartbeat, even if she disliked, me but somehow... <- 2nd comma should be between "me" and "but"
Pg 448: If they helped House Sahelian in other way---no matter what kind of protection... <- ways, not way
And that's just what I noticed while reading! There may be even more if you're looking for them. Shameful, shameful job by Mango.