As Tan Lin says, Tender Buttons is an index:
As Gertrude Stein recognized in Tender Buttons, which constitutes the first literary work of non-fiction to function like a blind index or (colorless) idea that has been typographically reset, the index is a poetical text and a fictional text it sits next to, like a caption in reverse, or a dining room table adjacent to an idea of sexuality, or the temperature of the room in which someone else’s writing took place.[1]