The movie focuses on Capote as he writes his ground-breaking 1965 novel, "In Cold Blood."
"I was shamefuly ignorant of Truman Capote," Jones told reporters in New York.
"I knew his name. It's sort of a romantic name that we don't get in the United Kingdom," he explained. "I remember him being a sort of exotic figure and I remember footage of him at Studio 54 in his sort of later, bloated years. ... I remember reading the script, thinking: 'This is fantastic! It's got the momentum of a thriller!"
Jones said he prepared for his high-profile role by keeping on a continuous loop in his trailer a short documentary made while the author was on the promotion trail for "In Cold Blood."
"The panic of playing someone so remote, in a way, it needs constant sort of gardening and that was the thing I relied on more than anything else," Jones said.