Most metal premise in the canon novels: a Twi'lek insurgency on Ryloth decides to assassinate the two most powerful beings in the galaxy, Palpatine and Vader, during a state visit. They pull off the impossible part. And then Lords of the Sith (Paul S. Kemp, 2015) spends its back half showing you exactly why it didn't matter.
Most Star Wars novels exist to hand you a win. This one is built to take one away. The Free Ryloth rebels get a genuine, impossible triumph, and the Emperor calmly wipes his hands and declares that nothing changed. No catharsis, on purpose. The rebels are brave, resourceful, and completely doomed, and Kemp never softens it. Isval, a former slave whose grief has curdled into something that scares her own allies, gives the book its emotional spine, and Cham Syndulla (yes, Hera's dad, this is where his fight takes shape) is the counterweight: a freedom fighter who refuses to become a terrorist even when principle costs him.
The central gamble is dumping the two Sith out of their fleet and onto a hostile planet for most of the book, hiking through forests and caves while Ryloth throws everything at them. On paper that's filler, and one giant-bug-nest sequence tips fully into video game territory. But every wave they cut through is a demonstration, and the accumulation becomes the argument: these are not men, and the harder the galaxy hits them, the more absurd the idea of hurting them becomes.
The real substance is the two of them together. Kemp writes Vader's hatred as a machine running on suppressed memory, and Palpatine spends the whole novel deliberately taking that machine apart, forcing his apprentice to relive his past as a "loyalty test." It's an abusive relationship dressed up as Sith theology, and the late reveal of how much Palpatine allowed to happen is the coldest thing in the book. Not the one to start with, and not the one to read when you need hope. But if you want to understand why hope was so hard to come by in these years, this is it.