But I can tell you that it was well worth reading. Between Shades of Gray is the story (not based on any one true story) of 15-year-old Lina, whose family is taken by pre-KGB Soviet secret police from their home in Lithuania and sent to Siberia. Horrible things happen. The ending is not particularly happy.
This is good storytelling. Author Ruta Sepetys does a good job unfolding the events in a not-totally-predictable manner. I also liked a theme that ran through much of the book: kindness matters. Lina's mother is in the habit of being kind to people, even when they are not kind to her, and it does matter in the end, even though Lina thinks it silly.
However, I did notice that despite the really horrible things that happen in this book, emotionally, it didn't pull me in as deeply as other books have (for instance, The Birchbark House). I couldn't pinpoint exactly why; perhaps just because this story is told fairly starkly.
Between Shades of Gray takes place during World War II (it begins in 1939), but tells a different, little-known part of the war story. It would make a good companion to World War II studies in the classroom. And if you've read Anne Frank: The Diary of a Young Girl, this would make a great comparison read.