The work "Heart of Darkness" by Conrad was written between 1898 and 1899, it was published for parts in the Blackwood Magazine. With this work Conrad found a new way of writing, in spite of the great effort he had to make to write it. The book is divided in three parts that belong to the preparation of the journey, the adventures of the journey and the return home.
  Conrad uses the description, an exclusive way to let us get into his world of nightmares and hallucinations.We also can see some optic effects that Conrad uses brilliantly.
  The symbolism in this book is quite naive, as in his other books.
  "Heart of Darkness" is a story that tells us a great experience in the Congo, but Conrad also makes a complex study of human emotions. Conrad usually speaks about issues that always interested him, like the human solitude and the relation between man and the power of the nature. We can find a constant obsession which is the civilised man in search of the limits of his nature.
  In this book, Conrad relive events of his own life, it·s a semi-autobiographic book. Conrad uses Marlow, a character of great importance, to tell his personal story. Marlow is a captain of an english ship, and is also the narrator of the book, he seems to represent a moral attitude: Conrad·s attitude. Nevertheless, the moral attitude of Marlow has also ambiguities. Marlow has no relation with the other sailors, he is different. Marlow represents the city life, but the strenght of the jungle have not been able to overcome Marlow, he doesn·t succumb to the strenght of the darkness.
  In the book Marlow meet Kurz, he is the combination of the darkness in the jungle and the darkness of the human being.
  Nobody can escape from the influences of the darkness.

Conrad wrote much books, here is his bibliography:

                   Twixt Land and Sea (Gutenberg text)
                    Almayer's Folly (Gutenberg text)
                    Amy Foster (Gutenberg text)
                    The Arrow of Gold (text at the English Server; 600K)
                    Falk (Gutenberg text)
                    The Heart of Darkness - HTML at Virginia and at Wiretap
                    The Heart of Darkness (original magazine version) (HTML at Gaslight)

                    The Inheritors, also by Ford Madox Ford (multiple formats)
                    Lord Jim -- HTML at Virginia and text at Wiretap
                    The Mirror of the Sea (Gutenberg text)
                    The Nigger of the Narcissus (HTML at Virginia)
                    Nostromo (HTML at Bibliomania)
                    Notes on Life and Letters (1921 edition) (Gutenberg text)

                    An Outcast of the Islands (illustrated HTML at Virginia)
                    A Personal Record --illustrated HTML at Virginia and Gutenberg text
                    The Rover (text at the English Server)
                    The Secret Agent : HTML with commentary and  HTML at Bibliomania
                    The Secret Sharer --HTML at Virginia and at Wiretap
                    The Shadow Line: A Confession (illustrated HTML at Virginia)

                    Some Reminiscences (Gutenberg text)
                    Tales of Unrest : HTML at Virginia and Gutenberg text
                    To-morrow (Gutenberg text)
                    Typhoon --  illustrated HTML at Virginia  and  Gutenberg text
                    Victory (HTML at litrix.com)
                    Within the Tides (Gutenberg text)
                    Youth and Two Other Stories (HTML at Virginia)