Short but very informative, this book is a prequel to The Force Awakens, giving us three short stories that add to the movie without giving away any spoilers.
I really enjoyed Finn's story the most, because it explains aspects of his training and your can see the struggle he's going through... The struggle that ultimately leads to his defection.
Rey's story is a little less intense but gives us more information on her day-to-day life on Jakku, as well as explaining how she got some of her skills.
Poe's story gives us more information about the Resistance and the corruption within the Republic. His story ends at just the right point, giving us the opening to the movie.
Overall, this is a wonderful collection that answers several questions that I had from the movie, as well as providing motivation and background for several characters.