How do you discern the true form of a religion if not from the writings or books?
Peace be on you.
Three things should be seen;
1- What does a religion say about God? --- i.e. His Oneness, Power, Knowledge, Perfection, Grandeur, Chastisement, Mercy, and other necessities, and properties of being Deity.
2- What does that religion say about the self of human and its teaching about usual human behavior,
=and whether there is anything that stands in the way of uniting the people in the bond of mutual relationship?
=or, does it teach him good morals,
= or does it drag him to shameless acts or result in such acts, and negates inborn modesty ?
= It should not have any teaching against common law of nature,
= It should not have any teaching which could not be practiced or result in dangers,
= It should not lack any teaching which is important to stop discord,
= It should teach such directives which declare God as grand benevolent and make strong tie with Him and take one from light from darkness ,and take one from ignorance to Presence and Remembrance,
3-That religion must not present a fake God or a God who lives only in stories of the olden days.
This God should not resemble with a dead, because believing such God due to good faith, not because He disclosed Himself. Believing such God will be like doing favour to Him. The God Whose Powers are not felt, and He does not show signs of Him being alive, believing Him is useless.
[Based on writing of Ahmadiyya-Muslim Promised Messiah -- The Mahdi (on whom be peace), Book Nasim e Dawat, vol 19 Ruhani Khazaen]