Walden enjoyed some success upon its release, but still took five years to sell 2,000 copies, and then went out of print until Thoreau's death in 1862. Despite its slow beginnings, later critics have praised it as an American classic that explores natural simplicity, harmony, and beauty. The American poet Robert Frost wrote of Thoreau, "In one book ... he surpasses everything we have had in America".
It is often assumed that critics initially ignored Walden, and that those who reviewed the book were evenly split or slightly more negative than positive in their assessment of it. But researchers have shown that Walden actually was "more favorably and widely received by Thoreau's contemporaries than hitherto suspected." Of the 66 initial reviews that have been found so far, 46 "were strongly favorable." Some reviews were rather superficial, merely recommending the book or predicting its success with the public; others were more lengthy, detailed, and nuanced with both positive and negative comments. Positive comments included praise for Thoreau's independence, practicality, wisdom, "manly simplicity", and fearlessness. Not surprisingly, less than three weeks after the book's publication, Thoreau's mentor Ralph Waldo Emerson proclaimed, "All American kind are delighted with Walden as far as they have dared to say."
On the other hand, the terms "quaint" or "eccentric" appeared in over half of the book's initial reviews. Other terms critical of Thoreau included selfish, strange, impractical, privileged (or "manor born"), and misanthropic. One review compared and contrasted Thoreau's form of living to communism, probably not in the sense of Marxism, but instead of communal living or religious communism. While valuing freedom from possessions, Thoreau was not communal in the sense of practicing sharing or of embracing community. So, communism "is better than our hermit's method of getting rid of encumbrance."
In contrast to Thoreau's "manly simplicity", nearly twenty years after Thoreau's death Scottish author Robert Louis Stevenson judged Thoreau's endorsement of living alone in natural simplicity, apart from modern society, to be a mark of effeminacy, calling it "womanish solicitude; for there is something unmanly, something almost dastardly" about the lifestyle. Poet John Greenleaf Whittier criticized what he perceived as the message in Walden that man should lower himself to the level of a woodchuck and walk on four legs. He said: "Thoreau's Walden is a capital reading, but very wicked and heathenish ... After all, for me, I prefer walking on two legs". Author Edward Abbey criticized Thoreau's ideas and experiences at Walden in detail throughout his response to Walden called "Down the River with Thoreau", written in 1980.
Today, despite these criticisms, Walden stands as one of America's most celebrated works of literature. John Updike wrote of Walden, "A century and a half after its publication, Walden has become such a totem of the back-to-nature, preservationist, anti-business, civil-disobedience mindset, and Thoreau so vivid a protester, so perfect a crank and hermit saint, that the book risks being as revered and unread as the Bible." The American psychologist B. F. Skinner wrote that he carried a copy of Walden with him in his youth, and eventually wrote Walden Two in 1945, a fictional utopia about 1,000 members who live together in a Thoreau-inspired community.
Kathryn Schulz has accused Thoreau of hypocrisy, misanthropy and being sanctimonious based on his writings in Walden, although this criticism has been perceived as highly selective.