This is basically Anakin/Vader's entire life in a short package, and from purely his point of view. You get the story as we already know it from the first six movies through different scenes with his thinking or feelings, but also some additional events, like when he and his Mom arrived on Tattooine, mentioning Clone Wars cartoon stuff, since this was written long before Disney took over, it mentions Prince Xizor and his dealing with him, and some other things that must have come from the comics or other novels at the time.