This is book #4 in the series, but it's not the fourth part. Apparently there's a short story, "Omega Night", and it contained both plot and character developments that significantly impact this book. However, even on the official author's website it's not listed between books 3 and 4. It's listed after the final book, among other "related works".

And the author doesn't really do a good job of recapping what happened, it's just an abrupt jump, and now Hope/Astra's angsting over a new crush that started during that book, freaking out over a danger to one of her friends that's due to events in that book, and a number of other sudden changes.

And these changes continue to casually come up over the course of the entire book, so that put a serious damper on my enjoyment of it.

Beyond that, the premise/setting was unique and somewhat interesting, but a lot of it felt like repeating "same song, different verse." Just marking things off a checklist. Astra has a crush that she doesn't want to act on (thankfully not the same one as at the end of book #3). Astra asks for advice, then ignores it in a way that could cause trouble for the one who gave it. Astra manages to get separated from her team (but thankfully not abducted this time). Astra makes mistakes and spends time berating herself. Important rules get massively broken but a loophole means it's okay. And the Perfect Defenses get destroyed via the most plausible method, which somehow no-one saw coming.

I did really like that, after introducing a terrifying Islamic terrorist supervillain in book #1, the author chose to introduce a character that showcases the more peaceful side of Islam. I wish the character was ongoing, but it doesn't look like he will be.

I really didn't like the friend drama for this book - it felt pretty contrived, but Astra was utterly poleaxed. Honestly, the number of times something relatively trivial knocks Astra so off her stride that she can't think straight for several days should probably be cause for serious concern among the team leadership.