Perhaps I'm a little biased against this book as I had to read it for school, but I could not find myself liking it.
The characters have some interesting chemistry with one another and have somewhat intriguing backstories, though much of the context of how the characters got here (especially with Florian and Alfred) is saved till near the end of the book, which can make you feel distant to them for the majority of the story.
In addition, I could not get past the dreariness that is persistent throughout the book. Look, I understand why the tone is so bleak, most of the events within the book are, or are based on, real things that happened in the Eastern Front of WWII. But the story is not very successful at making the rest periods between events seem any less miserable than the events themselves, which leads to it feeling like one, tedious exercise in human misery.
In the author's note at the end of the novel, Sepetys preaches that these are stories that need to be told, that she wished to give a voice to the countless innocents swallowed up by war, and indeed she does accurately illustrate the terrible things that these victims go through, yet she does it in such a way that the more the story goes on, the more demoralized you become to these horrors. In the beginning of the novel, we see a young fifteen year old named Emilia about to be raped by a Soviet soldier, before being saved just in time. This has a profound impact on the reader as it is told in such a tragic and fearful way from Emilia's perspective, yet as the story progresses you see babies getting smashed against the hull of the ship and barely bat an eye. The horrors of war are packed so closely together with such little breathing room between them that one simply cannot empathize with the tragedies unfolding in front of them after a point.