I loved Salon.com's review. They hated it, opening by saying, "If you care only about whodunit and not about how and why, “The Assassination of Jesse James” isn’t for you. Then again, if you care even remotely about how and why — or even just about staying awake — “The Assassination of Jesse James” really isn’t for you. There’s so much process here that there’s barely a story," calling it "so finicky it feels more like a doily than a western" and closing with this: "It may be the first time we’ve been asked to watch a book on tape."
Slant Magazine gives it 3 out of 4 stars and condemns those who say it's too long with this:
That Jesse James, brazenly affected and acutely interested in investigating the notion of personal and collective myths, doesn't resound with full, heartbreaking intensity until its climax and coda will likely prove too long a wait for those less enamored than Dominik with the seminal, plaintive, demanding westerns of Robert Altman and Terrence Malick, among others. To this impatience, the film has an apt reply, courtesy of Schneider's Dick: "Poetry doesn't work on whores."Rolling Stone gives it 3 1/2 out of 4 stars and says, "this quiet wow of a Western sneaks up as one hell of a satisfying surprise. Artfully exciting and compulsively watchable even at a butt-numbing 152 minutes". Slate titles their review, "You Can Give a Movie a Long Title but That Doesn't Mean It's Good". Empire Online gives it 5 out of 5 stars and calls it "An extraordinary and visionary study of a legendary murderer’s famous fate". Time Out calls it "stunning" and closes by saying, "it’s a journey of immense emotional foreboding and, flabby coda aside, a red-raw classic." Roger Ebert gives it 3 1/2 out of 4 stars, opens by commenting on the "homosexual undertones" and closes by defending its length: "Yes, it is long, at 160 minutes. There is a sense that an epic must have duration to have importance." The Rotten Tomatoes critics score is 76%.