Alternately funny and dark, How to Succeed in Evil: The Novel, is the story of Edwin Windsor, Evil Efficiency Consultant. A biting satire of both modern business and the conventions of the superhero genre.
This is new content, distinct from the original podcast episodes that have been up on podiobooks since 2006. While the novel is contained within the original podcast story arc, there's a lot more depth. Many new characters, much subplottery and (to use a technical term) it's funny as balls. Among other things we get to know Dr. Loeb a lot better.
If you love one, you'll love the other. But to put it in some kind of perspective, the original podcast episodes might be best thought of as really good notes, character sketches, etc. But maybe that's downplaying them a bit as they were good enough to win a Parsec award?
Also the Original Podcast Episodes have a lot of rich sound design in them. How to Succeed in Evil: The Novel is more of a traditional audiobook.