Takes place a few years after the prequel movies showing a younger Tarkin before becoming Grand Moff. While dealing with a crisis that affects the Empire and it's secret project, Tarkin reflects back on his life. Including his relationship to the Emperor and Darth Vader. 
 It's hard to show a villain's perspective without 'domesticating' them. The book establishes how Tarkin gained his reputation and his motivations without damaging his villain image. Unfortunately I found the opposite with Darth Vader. Varder talks too much which adds character but at the expense of his mystery and menace. The Emperor's was shown with an ultimate goal that motivates his need for power which I found intriguing and wanting to know more about. 
 I'll only recommend for Star Wars fans. It's part of the new canon so it's a good time to get started before it gets too big. Hints of an earlier book and episodes from Star War Clone Wars which I haven't read or seen but didn't feel that I missed much.