Sometimes in his rooms at Oxford, Lewis would play a parlor game, asking a visitor to pull any book out of his extensive library and read aloud a few lines. Lewis would then proceed to quote the rest of the poetry or prose verbatim for pages. For instance, Kenneth Tynan, who became a well-known English dramatist and critic, told of an encounter with Lewis during a tutorial at Oxford. Tynan said, "He had the most astonishing memory of any man I have ever known. In conversation I might have said to him, 'I read a marvelous medieval poem this morning and I particularly liked this line.' I would then quote the line. Lewis would usually go on to quote the rest of the page. It was astonishing.From C. S. Lewis's Case for Christ by Art Lindsley.
"Once when I was invited to his rooms after dinner for a glass of beer, he played a game. He directed, 'Give me a number from one to forty.' I said 'Thirty.' He acknowledged, 'Right, go to the thirtieth shelf in my library.' Then he said, 'Give me another number from one to twenty.' I answered 'fourteen.' He continued, 'Right. Get the fourteenth book off the shelf. Now let's have a number from one to one hundred.' I said 'Forty-six.' 'Now turn to page forty-six. Pick a number from one to twenty-five for the line of the page.' I said, 'Six.' So, he would say, 'read me that line.' He could always identify it -- not only by identifying the book, but he was also usually able to quote the rest of the page. This is a gift. This is something you cannot learn. It was remarkable."
InterVarsity Press, ISBN 0-8308-3285-8