Complex sentence: Damon Knight in "The Futurians" indicates James Blish at that time felt Fascism was interesting in theory, if repellent as it was then being practiced, more solid is that Blish admired the work of Oswald Spengler.
Split into simpler sentences: Damon Knight in "The Futurians" indicates that Blish at that time felt Fascism was interesting in theory, if repellent as it was then being practiced. More solid evidence is that Blish admired the work of Oswald Spengler.