Nietzsche acknowledged himself expressly that Zur Genealogie der Moral [On the Genealogy of Morals, 1887] was a sequel to Jenseits von Gut und Böse [Beyond Good and Evil, 1886], and he does refer the reader to many passages from his earlier works, which implies that one ought to read those first before embarking on a possible misunderstanding of Zur Genealogie der Moral, which is often read erroneously in isolation. Kaufmann makes the general observation that Nietzsche “presupposed not only a passing acquaintance with his earlier books but actually a rather close study of them” and recommends that the reader ought to read s260 of Jenseits von Gut und Böse and s45 of
Gallagher, David. "Zur Genealogie der Moral". The Literary Encyclopedia. First published 10 August 2011; last revised 30 November -1.
[http://www.litencyc.com/php/sworks.php?rec=true&UID=8931, accessed 25 April 2015.]