Previously, the AskHistorians podcast had an episode about Fascism, in which /u/AnnalsPornographie interviewed /u/commiespaceinvader. Commiespaceinvader also spoke frequently about Paxton's book in the episode, and included a list of additional books that sought to clarify, classify, or contextualize fascism. You can find the list of books listed by Commiespaceinvader here. The list contains both historical and contemporary treatments of fascism.

This is not to dissuade from further answers, as much more can be said on the subject!