Complex sentence: The Secret History of the American Left, From Mussolini to the Politics of Meaning is a book by Jonah Goldberg in which he argues that fascist movements were and are left-wing.
Split into simpler sentences: The Secret History of the American Left, From Mussolini to the Politics of Meaning is a book by Jonah Goldberg on the alleged origins and nature of fascist movements. In the book, Goldberg argues that fascist movements were and are left-wing.