Though I've mostly only read books from 21st century authors, I can say without doubts that these three authors are perhaps the greatest authors of the 20th century.

Number one is Williams Shakespeare, as expected. The genius of writing himself. His works continues to be used decades after historical demise. There is hardly any one who had passed through the four walls of an institution of learning that have not, in one way or another, come across words or quotes from his book. The ones I can remember are Romeo and Juliette, Macbeth, Hamlet and the Tempest.

Number two would be William Faulkner who is, I think, the only Mississippi-born Nobel prize winner. Such was the uniqueness of the man. Some of his works includes soldier's play, a fable and sartoris.

My number three is Charles Dickson. The works I love the most written by this great author are Oliver Twist, the chime and Great expectations. The one I loved the most is Oliver Twist. Reading it alone brings so much memories about my younger days when there were less worries. The first copy I had was a coverless, almost forgotten piece but it did nothing to reduce the excitement I felt.

So, there you have them. I wish you had asked about the 21st century though. Nevertheless, these are great authors and we are blessed to have their works within our grasps.