Quick-take: The Sith are the main characters in a very complex story.
Before Emperor Palpatine, Darth Vader, or even Darth Maul, there was Darth Plagueis. Without his efforts in the background, there may not be a Galactic Empire with Palpatine on the throne. This book starts around 30 years before Episode 1: The Phantom Menace.
Darth Plagueis is one of the last Sith Lords. I initially thought this was because they are suppressed, but apparently, that is just by design. For every thousand Jedi, there may be a single Sith. We are all familiar with the lore: Jedi follow the light side. Sith follow the dark side.
But... why? The book doesn't quite explain that. We basically follow Hego Damask (aka Darth Plagueis) and his apprentice, Palpatine (aka Darth Sidious) on their quest to acquire influence.
I never really considered how many business dealings Sith Lords must have. It makes sense. Political endeavours and hiring assassins can be expensive. Sith caring deeply about politics was new to me. Essentially, anything that can lead to more money and more influence, they try to become very skilled at. In fact, Darth Plagueis mentioned how he shuns women and is an eternal bachelor because women are just a distraction from power.
So obsessed with power, Plagueis attempts the 1 problem he knows can stop and will ultimately stop him: his own mortality. I thought this would cover more detail, but it was basically side stories throughout the book. The majority of the book covered Palpatine's schemings.
All in all, this book was an enjoyable 3/5 stars. If you really like Star Wars, this is a good book for you. I do not recommend reading this unless you are well-versed in Stars Wars trivia. Very little is explained. Planets and seemingly minor characters are frequently rattled off with no introduction.
This gets a 3/5. I may prefer an "easier" Star Wars book if I was to pick up another.