I really don't see why people think "Heart of Darkness" is such a great book

Are you talking about the book? Because I don’t remember the ‘savage’ and ‘civilized’ dichotomy being important thematically; I remember it as foreshadowing and ironic external reflection of the internal conflict.

You don’t see a lot of people reading The Nigger of the Narcissus on the bus or subway these days.

Nor in those days, allegedly. Found this tidbit in the Wiki article:

Which people think Heart of Darkness is a great read? I tried to read this on my own and tossed it aside - after having been told by at least a score of other english majors that it was terrible. One of the professors at our college was extremely lazy and only used that book for critical analysis of literature, so I knew many people who had spent an entire semester on the book. Who told the OP that it was great?

Lots and lots of English Majors at Uni, people I know who like books; and rather a lot of people in this thread whose opinions agree with theirs- I didn’t make up the assertation that HoD is a “Great Book” out of thin air.