Complex sentence: In 1977, Ballantine set up Del Rey Books as a science fiction and fantasy imprint under the editorship of Lester del Rey and his wife Judy-Lynn to rival Donald A. Wollheim's launch of specialist science fiction publisher DAW Books.
Split into simpler sentences: In 1977, Ballantine set up Del Rey Books as a science fiction and fantasy imprint under the editorship of Lester del Rey and his wife Judy-Lynn. This may have been a response to rival Donald A. Wollheim's launch of specialist science fiction publisher DAW Books.