system
Given the following post, respond as if you're commenting on Reddit:
human
How can I know whether I'm reading works totally by Frederick Nietzsche or works changed his sister?
gpt
You buy books published by a university press. 

Generally though, the works edited by Elisabeth are 'The Will To Power ' and some sections of 'The Antichrist'. 'Towards the Genealogy of Morals' and 'Ecce Homo' should be fine as well. His earlier work, published before his sister took over should be fine too (though there are quite a few horrible translations).