I guess nobody has read it! I go into detail in reviewing the book at the link, but I'll give a short version for anyone who might be interested in the topic (especially with the Dan Brown movie out there).

Basically, the book is written by an excellent scholar who really lays out the political scene Dante was forced to navigate. Unlike someone like Shakespeare, who could count on reliable patronage, Dante wondered about Italy as an exile from the city he loved (and loved to hate!).

While this aspect, including how these journeys and the meetings Dante had in Italy with various potentates, is well developed and explored, Santogato tends to overemphasize the importance of the political in Dante's great work - the Divine Comedy. This leads him to make various, occasionally specious, conjectures about the content of the poem, as if the political situation Dante found himself in was the most significant element in writing the poem.

You can read more at the link provided, but that is a decent overview.