I saw Capote on opening night and it's great.  It's about the period of time in which he wrote "In Cold Blood" which was the first "non-fiction novel" about a Kansas family who were killed by two men.  Truman went to Kansas to write the book, and befriended the killers, even to the point of feeling romantic towards one of them.  He also offered them financial assistance with lawyers for their appeals... but the case dragged on and his novel needed an ending - and for the novel to be a great novel, the ending had to be their execution.  So, Truman was torn between feelings for the men as well as his professional need to see them executed.

Personally, I think the writing of the book "In Cold Blood" killed Truman as well.  It took so much out of him.  It was a high point in his literary career that he felt he could not achieve again.  He was contracted to write "Answered Prayers" but only a few chapters which were published in a magazine ever surfaced after his death in 1984. 

He was an outrageous character.  "Answered Prayers" was written from stories about famous people he knew.  When the chapters were published, the famous people recognized themselves and alienated him.   His death was no doubt brought about by alcoholoism and he was only about 60 at the time.  He'd show up smashed on television interviews and talked of smoking "thai stick" at Studio 54...  He was unique and a genius.  It's a shame that the film only deals with the "In Cold Blood" period of his life because the before and after were equally interesting.