Complex sentence: In addition to his fiction, Brunner wrote poetry and many unpaid articles in a variety of publications, particularly fanzines, but also 13 letters to the "New Scientist" and an article about the educational relevance of science fiction in "Physics Education".
Split into simpler sentences: In addition to his fiction, Brunner wrote poetry and published many unpaid articles in a variety of venues, particularly fanzines. He also published 13 letters to the "New Scientist" and an article about the educational relevance of science fiction in "Physics Education".