Complex sentence: West's writing career spans two periods, the first half as a science fiction short story writer and the second half as a non-fiction book author: the former from 1961 to 1980, and the latter essentially from 1980 to 2007.
Split into simpler sentences: West's writing career spans two periods, the first half as a science fiction short story writer and the second half as a non-fiction book author. The former from 1961 to 1980, and the latter essentially from 1980 to 2007.