Complex sentence: He avidly read leftist journal "Politics", remarking that it "answered to and developed" his interest in anarchism, as well as the periodical "Living Marxism", published by council communist Paul Mattick.
Split into simpler sentences: He avidly read leftist journal "Politics", remarking that it "answered to and developed" his interest in anarchism. He also read the periodical "Living Marxism", which was published by council communist Paul Mattick.