Great book. I was a little dubious about this book. After the last book being slightly sub-par (good instead of great), and Thrawn's character in Rebels bring more Imperial then any other incarnation of him. I was not sure what to expect from this book. I am glad to say I loved it and could not put it down.
The story takes place a week before the finale of Rebels season 3. Thrawn is seemingly brought in as a pawn of Tarkin, to use make a grab for a certain battle station. Then Thrawn's loyalties are brought into question when his own people arrived on their own mission bringing with a a certain person not seem since book 1 and an enemy threat. Also not all threats to the Empire are external.
It is interesting that Thrawn is a much an outsider to his own people as he ever was in the Empire. In Rebels I saw Thrawn's ruthless side, but in the book I am shown his loyalty to his crew and subordinates and in turn their gratitude and loyalty back to him. A few interesting characters and names to watch out for as well an honorable mention of another Timothy Zahn created imperial character.
A great ending to this Thrawn trilogy, but is this the end of him? For some who was not known for his political savvy, he has loyalties in the Imperial military and has place key individuals how would have continued to climb higher since his disappearance. Also his own agenda has yet to be revealed. I might be wishful thinking but I truly believe their is more to come.