I'm interested in Jim's interpretation of Nietzsche [as there are many ways of viewing Nietzsche's work].
It seems to me that Jim first came across mention of Nietzsche in Kerouac. But I would say that the treatment of Nietzsche in Norman O. Brown's 'Life Against Death' was the most important influence on Jim's interpretation of Nietzsche. That and possibly Colin Wilson's sketch of Nietzsche in 'The Outsider' filled out Jim's picture of Nietzsche.
Brown's book was very important as it seems that Jim followed up many of the books Brown has in his Bibliography.
Basically, Brown's Nietzsche wants to rid mankind of repression, so that the Dionysian nature can come through. This is a rather distorted reading of Nietzsche though, being very Freudian.