Thrawn is a great Star Wars book that stands on its own. But the little nods and winks Timothy Zahn makes to Thrawn's old life in the Expanded Universe novels — and to the events in Rebels, where Thrawn is currently the main antagonist — add another layer of delight. You should definitely read Thrawn (and watch Rebels), but if you don't have time to go read a hundred EU books and watch three seasons of a cartoon, we've collected the major additions to the new Star Wars canon, as well as the threads planted in Thrawn for later stories.
Image: Star Wars Rebels, Disney/Lucasfilm
[Note: There are some spoilers here, but we've avoided most of the novel's main plotline. But seriously, just go buy the book already.]
Thrawn is effectively a prequel to season three of Star Wars Rebels. So events like Rebels making his flagship the Chimaera again don't make this list, but Lothal, Governor Pryce, Wulf Yularen and other aspects of Rebels all play important roles in the book. I'll hit some of that stuff here, but if you like Rebels, again, you really should just pick this book up.
Still, if you haven't watched Rebels, Thrawn is easily read without knowing anything from the show. It's a prequel that is truly its own story, and not just an excuse to throw out references to later material for fans.
Thrawn in his Chiss Expansionary Defence Force uniform (Outbound Flight cover by Dave Seeley, Del Rey)
Thrawn and the Chiss
Pretty much everything that was true about Thrawn's race, the Chiss, is true again, including the fact that the blue-skinned, red-eyed aliens are a fairly strong power in the Unknown Regions. Now, just as when we first met them in the EU, the Chiss Ascendancy rules a portion of the Unknown Regions and have a strong military with the inviolate rule that no preemptive strikes be taken. One of their languages, used fairly commonly in the Unknown Regions and their borders, is once again named as Sy Bisti. Chiss eyesight is also better than human eyesight, even getting close to seeing the infrared spectrum.
All of that has moved from old Expanded Universe to the new Star Wars canon pretty much intact. Slightly new is the idea that the Chiss have reached the level of urban legend/myth among the people who live near their area of the galaxy. One of the main characters of Thrawn is Eli Vanto, a young Imperial officer who was born in Wild Space, which borders the Unknown Regions. As a result, he speaks Sy Bisti and knows of the prowess of the Chiss from the local myths. However, just as before, the Chiss know far more about their neighbours than they do about the Chiss.
Additionally, the reason given for Thrawn leaving the Chiss is the same as his EU counterpart — he was exiled because he broke the "no preemptive strikes" rule. The opening chapter of Thrawn is almost identical to Zahn's 1995 short story "Mist Encounter". That means that Major Wyan, Colonel Mosh Barris, Captain Voss Parck and the ship Strikefast are all brought back in their original roles of introducing Thrawn to the Empire and the Emperor. (There are some subtle changes that make sense within the new canon, like using Clone Wars-era ships types, for example.)
In what is actually a very smart subversion of what EU fans were expecting — we all know Thrawn was exiled and why he was exiled — Thrawn alters its eponymous lead's motivations slightly. As before, Thrawn wants security and safety and sees the Empire as a better way to fight dangers than the Republic was. He basically thinks the Republic was useless in a fight and, while the politics and corruption of the Empire frustrates him, their military might and control is useful to him.
But now Thrawn's exile was a ruse. Thrawn was sent by the Chiss to gather information about the government next door. When the Emperor refused to have Thrawn as a counsellor, he took a job in the Imperial Navy in order to further his goal. The position helps him keep the Empire strong, but also always allows him to do what he thinks is best for the Chiss.
As he did in the old EU, Thrawn recruits humans to his cause and sends them back out to Chiss space. In this case, Eli Vanto is eventually sent by Thrawn to the Chiss. It's both a way of exchanging information and Thrawn's way of making sure everyone is strong enough to fight whatever dangers lurk out in the Unknown Regions. Vanto is met by Chiss admiral Ar'alani, who was Thrawn's superior and ally in the EU. We still don't know anything specific about the threat, merely that there is evil somewhere out there and it is bad enough that Thrawn will do anything to stop it.
It's worth remembering that the Aftermath novels have said that Palpatine is obsessed with finding out what's lurking in the Unknown Regions and is sending a significant amount of Imperial power out there. We also know that Thrawn shares his knowledge of the region with the Emperor — everything except the information about the Chiss. What everyone finds out there had better not be the Yuuzhan Vong (as it was in the EU) or I will lose it. Most fans are assuming it's where the Imperial remnant — who fled to the Unknown Regions after the Rebel Alliance kicks their asses and became the First Order — picked up Snoke.
Demanding its own book, novella, short story, whatever is the news that Thrawn met General Anakin Skywalker during the Clone Wars. They worked together in some sort of engagement in the Thrugii System (a locale from the EU that is now presumably closer to Chiss space in the new canon than it was in the old) and Thrawn was able to deduce even then that Anakin was under thrall to Palpatine. Whether or not Thrawn knows that Vader is Anakin is left unclear, but it's Thrawn, so I assume he totally knows.
Thrawn's time training in the Imperial military puts him under Commandant Deenlark from the new canon novel Lost Stars. And he gets some troublemakers sent to Skystrike Academy, which is where Wedge and Hobbie defect from in Rebels.
Rebels established that Thrawn attained the rank of Grand Admiral after the Battle of Batton, where he led forces against a group of rebels. The rebels died, but so did a lot of civilians. Thrawn makes Batton the last move in a long chess match between Thrawn and a criminal-mastermind-turned-Rebel named the Nightswan. It struck many as odd that Thrawn's career-making battle would have so many unnecessary casualties, so Thrawn makes clear that he tried to avoid them; it was a selfish action by future Governor Arihnda Pryce — often seen in Rebels — that caused the many, many deaths. Thrawn knows it, and Pryce knows he knows it, but Thrawn doesn't have any proof. But he's not happy about it.
Thrawn's ally from early on is Colonel Wulf Yularen, whose Imperial Security Bureau position helps the unconnected alien out. Thrawn is fairly awful at politics — well, specifically the full-contact sport and nepotism party that is Coruscanti politics. He always wins, but he makes connected people look bad, and his promotions usually follow court martial proceedings.
Thrawn with Pryce and Kallus in Rebels
Since the old EU got junked, Palpatine's non-human attendants and other smaller things gave the impression that the new canon Empire might hate non-humans a little bit less. Thrawn throws that out the airlock. Instead, everyone give a big warm welcome to the old EU's love of characterising the Empire as anti-alien, classist, and very, very corrupt.
Thrawn reveals that even if Palpatine himself doesn't care about aliens (Palpatine cares about himself and his power only), the rest of the Empire has a very clear bias. Thrawn's rise to power is faced at every turn by people not happy to see a non-human advance. Thrawn gives what I would call a justification for the racism rather than a reason: The Clone Wars were bloody and awful and the Separatists (the faction that lost) were mostly non-humans. So everyone's content to generally blame all non-humans for the war and the resulting devastation. That's obviously illogical and is clearly a justification for bias, but it's unfortunately plausible.
Thrawn pairs this with a bias in the Empire's government for the connected and those from Core Worlds (like Coruscant) rather than people from more "primitive" Outer Rim (Tatooine) or Wild Space (where Eli Vanto is from). Turns out the Empire — gasp! — is very corrupt. Who you know is most important and most people are lining their pockets. Pryce's rise to Governor of Lothal is detailed heavily in this book and she faces obstructions for the same lack of connections, and suffers from bias for being from an outlying world. Also mentioned as a little shout-out for Rebels watchers is a reference to Governor Azadi retiring "against his will" and an explanation of how Minister Tua got picked to act in Pryce's stead (and why). Admiral Konstantine also gets a brief appearance prior to Pryce asking for Thrawn's forces to replace his in Rebels.
We also are reminded that the Empire uses slave labour, Wookiee slaves especially. A ship full of Wookiee slaves is intercepted en route to, where else, the Death Star. Thrawn, rightfully, thinks the Death Star is a hideous waste of time and resources. Unfortunately, it is not his Empire. It belongs to the melted man with the lust for power.
Zahn brought back some things you wanted. But not even close to everything that fans really wanted (Del Rey).
This is a very minor bit, but early on in the book Emperor Palpatine takes Thrawn into a garden where "small trees with shimmering bark stand at the periphery like sentinels of privacy". Longtime fans will remember that trees with colour-changing bark were a favourite of Palpatine's in the old EU. The Ch'hala trees were both pretty and also a giant spy network, recording and transmitting everything that happened in front of them. Zahn used them in his original books as an important source of information, and if this wasn't a reference to them, I'll eat my hat (Thrawn describing them as "sentinels of privacy" is what sealed it for me).
In the very first pages of the book, there is an improvised explosive made with blaster packs with the "sturm dowels" pulled out. "Sturm" is a favourite name in Star Wars, popping up a fair amount. The first instance is Zahn naming one of Talon Karrde's pet vornskrs "Sturm" in his first Star Wars novel, Heir to the Empire.
But an overloaded sturm dowel was used by Zahn in Specter of the Past and the short story "Mist Encounter". (As mentioned above, the first chapter of Thrawn is basically just "Mist Encounter", slightly retooled.) It involves Thrawn, alone on the world he has been exiled to, utterly destroying an Imperial landing party. His tactics are impressive enough to gain him entry into the Imperial Navy, but we'll get back to that chapter in a bit.
In the old EU, doonium was a metal used to make starships. In the new canon, it's a metal that is worth a lot of money, and acquiring it and the mines that produce it drive the plot. It will shock no one to find out that large amounts of this metal are being bought by the Empire and sent to the location of a large, unnamed secret project (*cough* the Death Star *cough*).
I hate to burst anyone's bubble, but Mara Jade, Talon Karrde and even Gilad Pallaeon are missing from Thrawn. However, Thrawn does bring back H'Sishi and her people, the Togorians. (Think... large cats walking on their back legs with a culture based on honour and warriors. Yes, another one.)
Through a series of events in Specter of the Past, H'Sishi ended up working for Karrde. In Thrawn, she shows up as the owner of Yinchom Dojo, where Pryce trains — and which, unfortunately for H'Sishi, is used by others in an anti-Imperial plot. H'Sishi isn't involved with it, but she's told to leave Coruscant quickly after it's discovered.
Welcome back to the canon! Please join your fellows over on this list.
Basically, a beckon call is a remote control for a spaceship and Zahn used the technology to good effect in Heir to the Empire in 1991. He brought the idea back for Thrawn, where the title character uses one, along with some Clone Wars-era droids, to really just mess some thing up in the usual, over-planned, steps-ahead, badarse way Thrawn traditionally does.