Like another comment said, your best source is going to be their own websites. But from an outsider’s perspective, their motive seems to be taking the good ideas from the Abrahamic religions (love your neighbor, do unto others as you would have them do unto you, etc) and replacing some of their worse tendencies (close-minded devotion to YOUR interpretation of God and anything less will send you to Hell) with their polar opposites: “Beliefs should conform to one’s best scientific understanding of the world” (Tenet V from The Satanic Temple’s website)
Like another comment said, your best source is going to be their own websites. But from an outsider’s perspective, their motive seems to be taking the good ideas from the Abrahamic religions (love your neighbor, do unto others as you would have them do unto you, etc) and replacing some of their worse tendencies (close-minded devotion to YOUR interpretation of God and anything less will send you to Hell) with their polar opposites: “Beliefs should conform to one’s best scientific understanding of the world” (Tenet V from The Satanic Temple’s website)