In 1965, reviewer George Steiner called In Cold Blood ‘‘more than a book; it is a happening.’’ He cited Capote's ‘‘superb journalistic skills’,’ and the resulting text was characterized as "masterful." Steiner reflected the sentiments of most critics, who were impressed by Capote's methods and engrossed by the story, which was written in such a way as to give, as Steiner noted, ‘‘psychological order to a piece of implacably authentic, documented life.’’ Frederick Dupee dubbed In Cold Blood ‘‘the best documentary account of American crime ever written,’’ and in the 1980s, Kenneth Reed, in his book, Truman Capote, wrote that In Cold Blood was a ‘‘virtually unparalleled triumph in creative reporting...supremely orchestrated in its progression and tone.’’ Helen Garson, another complimentary critic, defended the lyrical ending of the book, reminding readers that the story ‘‘is not purely documentary'' and asserting that the ending seems "completely appropriate to the artistic intent behind the novelistic element.’’
The book has had its share of detractors as well. Critics who questioned and found illegitimate Capote's investigative and research methods pointed out that he never used any kind of recording device during interviews or even took notes. Capote claimed he had trained himself over the years to absorb a large amount of material aurally and then transcribe it later with astounding accuracy. Indeed, when he began to write In Cold Blood, Capote had amassed thousands of pages of notes. Reviewers who criticized elements other than the research methodology complained, as did William Phillips of Commentary, of a ‘‘contrived shifting of scenes giving off an aura of fictional skill and urbanity.’’ They claimed that the book was trying too hard to be poetic, novelistic, and true to fact, to a seemingly contradictory end. Stanley Kauffman wrote in The New Republic that the book was "without the finesse, of which, at his best, [Capote] has been capable, and it is residually shallow.’’ Richard Poirer asserted in his 1999 book Trying It Out in America: Literary and Other Performances that with this book, Capote has earned a ‘‘minor place in American letters.’’ Although the bulk of critics have been kind to Capote and to In Cold Blood, there will be those who, like Phillips, regard the book as merely "high class journalism,’’ not firmly rooted in or accepted by the conventions of either reportage or novels.