While I mainly got into Star Wars through reading the EU books (specifically Young Jedi Knights), I never read The Heir to the Empire trilogy aka The Thrawn Trilogy. Even still, I was certainly aware of the popularity of the Imperial Grand Admiral. So, when his official arrival to canon was confirmed during Star Wars Celebration 2016 with the Rebels season three trailer, I decided to hop on the bandwagon. Thrawn by Timothy Zahn (a first in the new Thrawn trilogy) was released in 2017 and is a great introduction to canon Thrawn. I cannot comment on how different the character is from the original EU version from the 90s but the canon book portrayal is slightly different from the Rebels portrayal. The book presents Thrawn as an observant military genius who is loyal to people under his command and, although he faces prejudice from Imperial personnel during his rise within the Empire, does not take slights thrown at him personally. He also seems to value life more than most Imperial commanders. Rebels Thrawn is more of a cut and dry villain though both portrayals capture what makes Thrawn unique, besides being a non-human among the Imperial ranks: his appreciation of art and culture and the sense to use them as weapons in war. Zahn’s military Sherlock Holmes has a novel structure that is also interesting, with intros at the beginning of each chapter from Thrawn.
Considering the name drop in The Mandalorian Chapter 13: The Jedi, it is not if Thrawn will make his live-action debut but when (and bets are on the announced Ahsoka series). I have no idea which Thrawn, book or Rebels, will appear on screen but it is worth the time to at least to know the backstory in canon of the Chiss Officer turned Grand Admiral of the Empire. And, given graphic novels are more accessible, I recommend the Thrawn by Jodie Houser and Illustrated by Luke Ross. It is a condensed adaptation of the first novel in the trilogy and covers all the main points of his backstory, including his association with Arihnda Pryce (who is another key character in Rebels seasons three and four and who gets her own backstory as well). Thrawn is the only graphic novel adaptation of the character’s canon novels so it is a perfect way to get some context without having to read the novels or even watch Rebels. Though I do recommend watching Rebels if you haven’t to familiarize yourself with other characters in that show. You can also buy the individual comic issues (there are six total) if you only buy digital comics or read if you are subscribed to services like ComiXology or Marvel Unlimited.
Along with Ahsoka, Thrawn is one of the most popular Star Wars characters that most people don’t know about. Unlike Ahsoka, he has not waited as long from being introduced as canon to appearing onscreen and Lucasfilm publishing is currently in the middle of his second trilogy release. Ahsoka hasn’t started filming so if you do want to start reading the novels, you have some time. The entire first Thrawn Trilogy (Thrawn, Thrawn: Alliances, and Thrawn: Treason) is great and will also give you some backstory on Thrawn’s relationship with Anakin Skywalker and Darth Vader. But if you just want to test the waters, the Thrawn graphic novel is a great substitute. I will caveat that the graphic novel, from what I can find, is not available in any other language except English so, if English is not your main or first language, the book is available in most translations.