Difficult to choose a star rating, because I loved the first 2/3 of the book and was really disappointed with the rest. The actual ending was abrupt and unsatisfying, and the last third was just crammed full of worldbuilding and clever space mechanics at the expense of story and character. I'm usually annoyed at books that get stretched into trilogies, but this book wanted to be a trilogy. I'm going with 4 stars, but that's just an average of an excited 5 and an angry 3.