Intellectually very challenging.
Even though it is a religious book for many people, it can be read as just a normal story.
It teaches one about how to live life, not by set of defined rules, but by providing a proper explanation and through understanding.
It's a book which is usually dated to 5000 years or 7000 years.
It`s a very well-balanced story, one can ignore parts which are not relevant to present society.