Complex sentence: Dennis Yates Wheatley (8 January 1897--10 November 1977) was an English author whose prolific output of stylish thrillers and occult novels made him one of the world's best-selling writers from the 1930s through the 1960s.
Split into simpler sentences: Dennis Yates Wheatley (8 January 1897--10 November 1977) was an English author. His prolific output of stylish thrillers and occult novels made him one of the world's best-selling writers from the 1930s through the 1960s.