As per the meaning of supply one of the ingredients is to establish that a particular transaction is in the course or furtherance of business. The sale of books, articles, mementos etc. to generate revenue is an incidental business activity subject to the provisions of GST.
Further, the rate of tax applicable to books and journals is NIL. Advancement of Religion, Spirituality and Yoga is regarded as charitable activity covered in the exemption notification, provided the organisation is registered under 12AA of the Income Tax Act.