The two things that ought to be remembered come Oscar time are probably the standout writing of Jeff Nichols as an American original, and the performance of Matthew McConaughey. The New York Times’ AO Scott makes it a “Critic’s Pick,” writing: The central image in “Mud,” Jeff Nichols’s deft and absorbing third feature, is of a boat in a tree. It’s the kind of phenomenon — a caprice of nature that is absurd but also wondrous — designed to enchant adventurous children like Ellis (Tye Sheridan) and Neckbone (Jacob Lofland), two Arkansas boys who discover the boat on an overgrown island in the Mississippi River. They also discover the fellow who claims to own, or at least inhabit, the vessel, a leathery loner whose name is Mud. Mud is played by Matthew McConaughey in the latest in a series of surprising, intense and often very funny performances following his escape from the commercial romantic-comedy penal colony. “Magic Mike,” “The Paperboy,” “The Lincoln Lawyer” and “Bernie” are all very different (and differently imperfect) movies, but in all of them, and in “Mud,” Mr. McConaughey commands attention with a variation on a certain kind of Southern character: handsome but battered, charming but also sinister, his self-confidence masking a history of bad luck and trouble. The Los Angeles Times’ Betsy Sharkey: Much turns on the clandestine adventure that follows, the boys’ excitement at being a part of it doing much to buoy the film. Besides, if Ellis believes anything, it is that Mud loves Juniper and Ellis is clearly moved by love. With matted hair, a cracked front tooth, sun-browned skin and blues eyes sparking mischief, McConaughey beautifully articulates with his honeyed drawl the very essence of a grizzled, determined romantic. It is the best work of the actor’s career, though virtually everyone in the film turns in sensitively drawn performances, particularly the boys. If you don’t know the name Jeff Nichols — if the writer-director’s singular voice, fierce and fearful in 2011′s “Take Shelter,” somehow eluded your notice — make note of it now. “Mud” should securely anchor this rising tide as a distinctive talent to remember. And Joe Morgenstern of the Wall Street Journal (you really must read the full review — that Morgenstern…): Mud’s charisma lies in the wide eyes of his beholders, a couple of 14-year-olds who come upon him hiding out from the law and other pursuers on a little island in the Mississippi River; his literal hideout is an abandoned boat nestled high in the branches of a tree, where it was deposited by a flood. The movie belongs to the teenage buddies as much as to the title character, and echoes of Mark Twain are neither accidental nor incidental. This coming-of-age story focuses mainly on Ellis (Tye Sheridan), who, like his best friend Neckbone (Jacob Lofland), lives on the banks of an Arkansas tributary, in a community of makeshift houseboats. Others may view Mud as nothing more than a scruffy murderer on the run, but the kids see him, at least for a while, as a romantic renegade living out a violent adventure in the service of undying love. He’s a marvelous figure, the product of flawless writing—more about that later—plus a brilliant performance that’s no less subtle for being theatrical. Mr. McConaughey is a past master of sparkly narcissism. That’s part of what pulls the boys into their hero’s wobbly orbit from the very first moment they see him up close, squinting in the summer sun with a cigarette in his teeth. But this portrayal, the best work of the actor’s career, goes far beyond picturesque poses. The man really is a romantic, richly nourished by self-delusion, and Mr. McConaughey, with his musical voice and commanding physique, sustains a delicate balance between Mud’s poetic yearning for his girlfriend, Juniper—she’s played to slatternly perfection by Reese Witherspoon—and his survival instinct, which prompts him to enlist his naive acolytes as accomplices to his escape. And then later: Motion pictures rich in character and language are often adapted from literary sources, but Mr. Nichols’s screenplay is original in the fullest sense of the word. It’s full of great phrases—Mud describes an evil rival as “the triple-six real-deal Scratch”—as well as great lines: “We knew to be afraid of snakes long before we ever got into this world,” Mud says, with an emphasis on the word “this” that bespeaks his private vision of another sphere. In three features over the course of six years, Mr. Nichols has offered a vision of American life that is regional, though never provincial. But “Mud” suggests that there’s nowhere he can’t go. It’s a movie that holds out hope for the movies’ future.