Literary critic Harold Bloom wrote that Heart of Darkness had been analysed more than any other work of literature that is studied in universities and colleges, which he attributed to Conrad's "unique propensity for ambiguity." However, it was not a big success during Conrad's life.   When it was published as a single volume in 1902 with two more novellas, "Youth" and "The End of the Tether", it received the least commentary from critics.  F. R. Leavis referred to Heart of Darkness as a "minor work" and criticised its "adjectival insistence upon inexpressible and incomprehensible mystery".  Conrad himself did not consider it to be particularly notable.  By the 1960s, though, it was a standard assignment in many college and high school English courses.
Marlow listens to Kurtz talk while he pilots the ship, and Kurtz entrusts Marlow with a packet of personal documents, including an eloquent pamphlet on civilizing the savages which ends with a scrawled message that says, “Exterminate all the brutes!” The steamer breaks down, and they have to stop for repairs. Kurtz dies, uttering his last words—“The horror! The horror!”—in the presence of the confused Marlow. Marlow falls ill soon after and barely survives. Eventually he returns to Europe and goes to see Kurtz’s Intended (his fiancée). She is still in mourning, even though it has been over a year since Kurtz’s death, and she praises him as a paragon of virtue and achievement. She asks what his last words were, but Marlow cannot bring himself to shatter her illusions with the truth. Instead, he tells her that Kurtz’s last word was her name.
Since Heart of Darkness remains a signal work of the Western canon, this debate is ongoing. Again, it seems that the central issue is the distance of Conrad from Marlow. The story of Marlow corresponds so neatly with Conrad’s own biography that it is easy to assume that Marlow registers Conrad’ own perspective, including his prejudices and perhaps racism. But on the basis of the novella alone, it is impossible to determine whether Conrad expresses his own views by simple transference or, as one might credit a great writer with doing, by lampooning the imperialists. Although the natives are often incomprehensible in the tale, they also are more innocent. To make one’s own decision about this issue, one should consider the overall themes of the work and how this issue relates to them—but also how Conrad would have expected his contemporary audiences, themselves of varying opinions about race and colonialism, to read his book.