Complex sentence: He selects the topics for his books by writing about things he wants to know more about, the advent of the Internet makes it much easier to do research than back when he first started writing books in the early 1990s.
Split into simpler sentences: He selects the topics for his books by writing about things he wants to know more about. The advent of the Internet makes it much easier to do research than back when he first started writing books in the early 1990s.