Except that David Filoni brought Thrawn back into canon when he made Thrawn the primary antagonist in the last two seasons of the cartoon Star Wars: Rebels. The cartoon version was not quite as powerful as Thrawn was in the books, but he was still fairly intimidating. Then, Thrawn's name was dropped by Ahsoka in the second season of the Mandalorian, suggesting that he will be the antagonist in her show when it releases sometime this year.
I was thus interested to discover that Timothy Zahn was writing more books (six in total, so far) with Thrawn in them, and that they were in line with Thrawn's reappearance in Star Wars canon. Ironically, the second trilogy takes place before the first one and establishes Thrawn as a much more sympathetic character than he is in Legends stories. In fact, taking the six stories all together, a completely different picture of Thrawn is formed--one where he is skillfully using the Empire in preparation to fend off an even greater evil.
I enjoyed the books as Thrawn is portrayed as a kind of Sherlock Holmes in science fiction space battles. Each book presents at least one mysterious adversary that Thrawn manages to outwit by the end while still exploring other deeper mysteries that underlie the larger narrative. I'm now a bit concerned that Thrawn's appearance in Ahsoka will be more of the canned villain type than the more nuanced character that I have come to know.
The book series is a niche within a niche within a niche, but I recommend it for those who either already like reading about Thrawn or who enjoy the more logically presented side of the Star Wars universe.