Warning: Spoilers follow
Published in 1903, The Call of the Wild is London's most familiar book and considered one of his best. Because the protagonist is a dog, it is often mistakenly thought to be particularly suitable for children. The hero, Buck, is a domestic pet who is abducted by thieves and sold to a trainer of sled dogs. In a series of episodes, Buck is forced to survive and adapt to brutal and cruel conditions. He is eventually acquired by a kind and loving—but exploitative—owner, John Thornton. When Thornton is killed by "Yeehat Indians," Buck returns to the wild. Images of death, cruelty, and Darwinian struggle abound. Of the new world Buck enters, London writes "The salient thing of this other world seemed fear." (Such dark themes are typical of Jack London's work, and he defended them in his essay "The Terrible and Tragic in Fiction.")
The University of Pennsylvania's Online Books Page  states that "Jack London's writing was censored in several European dictatorships in the 1920s and 1930s. In 1929, Italy banned all cheap editions of his Call of the Wild, and Yugoslavia banned all his works as being 'too radical.' Some of London's works were also burned by the Nazis." (These regimes may have been reacting to Jack London's reputation as an outspoken Socialist rather than to the content of the book, which, unlike some of his other novels, has no overt political message).
In 1960, critic Maxwell Geismar called The Call of the Wild "a beautiful prose poem." Editor Franklin Walker said that it "belongs on a shelf with Walden and Huckleberry Finn". E. L. Doctorow called it "a mordant parable... his masterpiece."
In 2001, The Call of the Wild was listed as one of the 100 best English language novels of the 20th century by the editorial board of the American Modern Library.