Mortimer Adler has found some special qualities that make a great book different from other books. One of the qualities of great books is that they are most readable. They never disappoint the readers. Great books contains more ideas per page than most other books. Each page of a great book contains such ideas which cannot be found in any other books. So, they can be read over and over again. Another fact is that great books can be read at different levels of understandings. They can be explained in different ways. While great books delight the adult minds, children find joy in them. Thus great books can be enjoyed by different people according to their level of understanding.