What is a great book?

Recently, I was recommending to one of my clients a great book entitled, The Seven Habits of Highly Effective People by Stephen Covey. Now, this client is a particularly discerning individual, and she challenged me as to whether or not the Seven Habits is truly a great book.  I said it was, according to a definition articulated by J. Rufus Fears (the late, great historian, scholar, teacher) which I am most fond.  According to Professor Fears, a great book has the following three essential qualities: • Great theme. A great book is concerned with themes and issues of enduring importance.
• Noble language. Great books are written in noble language, language that elevates the soul and ennobles the mind. It is not the specific language, say Latin or English, that is noble. Any language can be used in such way that it conveys ideas and emotions powerfully and memorably.
• Universality. A great book is “a possession for all time” (Thucydides). It speaks across the ages, reaching the hearts and minds of men and women far removed in time and space from the era and circumstances in which it was composed. Thus, a great book summarizes the enduring values and ideas of a great age and gives them as a legacy to generations to come.Also for Fears, what ultimately makes a great book is its ability to speak to each of as individuals.  I also find this to be true.   As we read a great book many times at various stages of our lives, it should provide guidance and personal wisdom to help us lead virtuous lives.By these measures, I believe that The Seven Habits does qualify as a "great book".  I can recommend it without reservation.  I hope it will speak to you, as it has to me.