If you're talking about the writer THEMSELVES, then you use the past tense, as you are talking about their private personality or nature.
However, if you're talking about a writer's technique which he uses in the piece of literature, you use the past tense.
"Shakespeare parodied many conventions of plays in his works. For example, in The Tempest, he uses the blah to blah blah blah blah"
I hope I've helped!