Shadows of the Empire by Steve Perry

Here is the untold story of the events that took place between the movies The Empire Strikes Back and Return of the Jedi: a novel in which Darth Vader still lives—and battles a villain as powerful and evil as himself.

All I can say is there’s a reason they didn’t make a movie out of these events, although the book is certainly written like the author is hoping they will. It’s already scripted down to the last blaster bolt.