This book disappointed me twice.
First it seemed to promise me a story about Code Girls (as the title would suggest), or at least girls who would spend a substantial part of their story finding out secrets that could threaten the UK (as the tagline "Can four girls protect a whole country?" suggests). That turned out to not be the case: not until roughly 70% in do the girls even notice that something is amiss. And the next 30% of the book still spends most time on unrelated subplots. The lack of tension build up during the story meant I was emotionally completely uninvested during the confrontation. The stakes are also much smaller than the tagline would suggest: Rather than safe an entire country, these girls unmask one spy. And while yes, he does get 50 people killed, nothing in the story suggests that he would have had a significant impact on the course of the war. This whole (sub)plot reads to me like it was haphazardly slapped at the end of the story to make sure it had some excitement, rather than a main plot or logical culmination of the character arcs.
Once I gave up on my hopes on a suspenseful story about code breakers, I tried to enjoy what this book seems to be aiming for instead: a story about friendship and love during war time. And even that fell flat. Despite this clearly not being the authors intention, after their introducing paragraphs the four main characters become near carbon copies of each other, with some (mostly informed or cosmetic) defining characteristics slapped on. In most interactions it felt like the characters could have easily swapped position without it being out of character for any of them. In fact that is exactly what happens in the story over and over, with the same scenes repeating in different arrangements. This lack of personality makes their friendship feel flat and meaningless. There were hardly any diverging opinions or behaviours that would let the girls learn from each other. There was no conflict, which seems very unlikely for 4 young ladies spending 4 years in close quarters in a constant state of being overworked. The main characters had no flaws to overcome. There simply was no development.
The romance was lacklustre and rushed, probably because 4 separate love stories needed to be told, leaving little room for building deep and complicated relationships. To avoid telling the same story 4 times, every love story does get its own little defining characteristic, which is great because the love interests don't get any defining characteristics of their own. Unless you count sweet Raf, who's personality seems to be "look how cute he doesn't speak English". This does not mean that scenes don't repeat, because they totally do. While it can be symbolic and beautiful to have scenes reference previous ones, that only works if there are enough differences, and it isn't done too much. In this case, it comes across more like the author ran out of inspiration and hoped nobody noticed she copy-pasted the same story.
So if this story is not about code breakers, and doesn't spend any time on interesting characters or character development, what is this book really about? The answer, apparently, is food. I do not think I am exaggerating much if I were to claim that more words are spent describing the many menus these girls come up with than on any of the love stories. Which could definitely be an interesting thing if the author went a little bit more in-depth into some of the crafty ways they manage to produce enough food to feed everyone while on rations. However just like with the love stories, the author seemingly goes for quantity over quality and prefers to just list the menus item by item. The result is familiarly uninteresting.
In the end, this book struck me as a directionless story written by an author who overreached by trying to do too many things at once and failing at all of them because of it. If possible I'd have given it 2.5 stars, as aside from being bland the story is not actively bad, it's mainly uninteresting.