Salt to the Sea is centred around a group of teenagers living through WWII, and their struggle to survive and board the Wilhelm Gustloff, the ship that will take them to safety. However, it isn't all plain sailing (pardon the pun) and a whole lot of adventure, hardship, and friendship unfolds. 
 I loved this book. Like, LOVED. 
 The plot was so obviously researched and accurate, which not only added to the realism but also the emotion that the book conveyed because the events actually happened. People lived through that. Throughout the book, I sometimes forgot about that fact but in the author's note at the end of the book in which Sepetys talked about the past surrounding the Gustloff, it just made the entire book even more harrowing and powerful. 
 Another thing I loved about this book was the characters. Each chapter has a different POV, belonging to one of the four main characters, either Emilia (a fifteen year old Polish girl), Joana (a Lithuanian nurse), Florian (an art conservationist from Prussia), and Alfred (a German sailor). 
 All of them are hiding secrets and are so fleshed out that I couldn't even hate the character I was supposed to, because they were just such a GOOD character. 
 Perhaps the reason why Emilia was my least favourite character was because I listened to it as an audiobook and the reader for her chapters had a voice that I couldn't concentrate on, so someone physically reading might have a different experience. 
 The reason why I have rated this 5 stars is also because it was educational but not in a textbook way. It never felt dull or info-dumpy yet I walked away from it having gained a lot more knowledge about WWII, even though I have been studying it for two years at school. Oops