Bogost's central insight is that games can encode playable representations of situations and even ideas, which supports a unique form of rhetoric, "procedural rhetoric". He argues that this can be (and has been, on occasion) used to make games into a expressive medium that goes far beyond entertainment, and in some ways even beyond other forms of expressive media.
Like other forms of rhetoric, procedural rhetoric is based on representations, but while visual or textual rhetoric merely shows the viewer or reader the representation, procedural rhetoric lets *you* engage with the representation, poking at it and interrogating it, and works its power through that interaction. Bogost covers a number of historical examples of games that make good use of procedural rhetoric to engage with issues ranging from tax avoidance to cold-war brinksmanship, as well as discussing where he thinks fruitful further development lies. On the latter point, he puts his money where his mouth is, so to speak, since he also owns a company that makes persuasive games, on issues ranging from presidential elections to food poisoning.
There are two basic audiences for this book. For those interested in how videogames can move beyond entertainment to other areas, Bogost presents a compelling vision of games as an expressive medium, and points to a wide range of things that can be done by thinking of games as playable representations. For media-studies scholars and rhetoricians, Bogost presents a strong case that procedural rhetoric is indeed rhetoric, but a new kind of rhetoric that existing discussion of film or written rhetoric doesn't quite account for.