The novel of Revenge of the Sith is canon. It aligns with the established Star Wars canon framework and adds depth and detail to the events depicted in the movie of the same name.
The plot of Revenge of the Sith centers around the final stages of the Clone Wars and Anakin Skywalker's descent to the dark side. It's a complex and intense story with lots of action and drama.
Well, for one thing, it combines two different eras of the Star Wars universe in an engaging way. Luke is from the original trilogy, and 'Revenge of the Sith' is part of the prequel trilogy. So when he watches it, there are all these connections that can be made. For example, he might see how the Sith's manipulation in the prequel era led to the state of the galaxy he was born into. It also allows fans to explore how Luke's Jedi training and beliefs would influence his view of the events in 'Revenge of the Sith', which is really fascinating.
Well, in some 'Luke watches Revenge of the Sith' fanfictions, Luke is brought to the time when the movie is taking place. So, not just watching but kind of experiencing it in a different way. There could be a fanfic where he tries to prevent Anakin's fall by interfering in the events, which makes for a really interesting read. It shows how Luke's presence could potentially change the whole Star Wars prequel trilogy's outcome.