Palpatine was born on Naboo. He was a Sith Lord in secret while rising through the political ranks in the Galactic Republic. He manipulated events and people from behind the scenes for a long time. Eventually, he revealed his true, evil self and transformed the Republic into the Galactic Empire, becoming the Emperor.
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.
Anakin Skywalker and Obi - Wan Kenobi are main characters. Anakin's fall to the dark side is a major part of the story, and Obi - Wan is his former mentor.
One of the best quotes is 'This is how liberty dies... with thunderous applause.' It shows the tragic irony as the Galactic Republic falls while the people, unknowingly, cheer for its downfall.