No, it's concealed because it's only available to the literate, leading me to assume it's somehow possibly beyond the reach of certain people.
One of the greatest Celtic warriors of all time was a woman, for instance. Did you know the Celts were/are a people with an amazing and rich mythology and culture, and not just a basketball team? Well, now you do. This is just an example of the treasures you might find concealed in books.