It start of the book hooks you in with the kidnapping of the Solo kids (that happened a lot to them) but it made me think that Leah was a lousy mother. She took the kids to a planet where kidnapping was a cultural norm. (Of course she didn’t know that since the planet was very secretive about it)
The main villain Hethrir was interesting: a Fierro (near human with striped hair and super healing) who was trained by Vader, abducted all adults from his world and forced them to watch while he bombed their world and their children. His Empire Reborn cult had interesting technology including lightsabers whose blades were powered by the force. He also had the interesting ability to smother other force users abilities.
The secondary antagonist Waru seemed to be more reminiscent of Star Trek rather than Star Wars. An interdimentional blob of a being trapped in our universe who formed a cult around them. The author did not explain much about this being except at the end, saying that hethrirs experiments pulled it out of its own universe and stranded it here, and all it wanted was to go home. But I don’t think so. This thing formed a cult around itself where people would come from all over to be healed. Waru would heal them, but occasionally they would die instead. The author stated at the end that Waru was absorbing the force from them, and if he got enough, he would give some back to heal them. Warus insatiable appetite and Hans experience witnessing warus killing of an ithorian child makes me think otherwise. Han describes the sound Waru made when the child died as satisfaction. Perhaps I am too suspicious, but I suspect Warus true plan was to use whatever power he had to heal people, and whenever they brought him a force sensitive, suck it dry and say whoops.
The guy murdered children and turned Luke into an unrecognizable jerk (much like the sequels did).
While it is only mentioned once at the end, the concept of Waru being from an anti-force universe stuck with me. I theorize that much like other interdimentional beings (mindflayer from stranger things and Bill Cypher from gravity falls) Waru destroyed all life in his own universe and sought to come here. Problem was, much like matter and antimatter, force and anti force don’t mix well, so Waru needed to get enough force to push his anti force back to his home universe so he could start plaguing the force universe without having to hide in the force nullified region of the Crystal Star. From Warus physical description it seems as if he is a scab or infected wound in the fabric of reality. Our reality having an alergic reaction to him.
Additionally, I get the feeling that Han may be Anti Force sensitive. In the book, he was the only person capable of fully resisting Waru and pulling Luke and Leah out of Warus innards. What if the reason for Hans luck isn’t mild force sensitivity, but extreme anti force ability? What if there is a universe out there where if our heroes were to go, Luke and Leah would be powerless, but Han, Chewie and Lando would be all powerful?
Sorry for the long read but I had a lot of thoughts.