Faulkner, William. Sartoris (New York : The New American Library, [1964]). Thomas Merton's Marginalia Collection.

A full-text version of the entire work (in a different edition) is available at:
https://archive.org/details/in.ernet.dli.2015.125862/page/n14/mode/2up.

An edition like Merton used is available to borrow:

https://archive.org/details/sartoris0000faul_o3m5.

Merton mentions Sartoris in his journals, see also:

See accompanying link to Bellarmine University library catalog for the publisher and other bibliographic information.