[Image description: photo of a page in the book Heir to the Empire, with this text highlighted:
"Thrawn smiled faintly. "You served too long under Lord Vader, Captain," he said. "I have no qualms about accepting a useful idea merely because it wasn't my own. My position and ego are not at stake here.""]
2nd book is great, he's ruthless but focused, even reasonable at times, and you watch the slow but inexorable evolution of his plan.
Then 3 breaks all the rules, from when he shows grace in accepting surrender, to when Luke escapes the beam, you see he's an imperial ruler who isn't really evil, he's properly efficient, he uses tools effectively to reach his goals and keeps pique and grudges mostly out of it.
The whole third book he plays the rest of the galaxy like a fine instrument, right up until his crescendo, and the few threads slip loose.