I'm baffled that this is Conrad's most acclaimed work. It does have technical merit; the language is beautiful; but the atmosphere wasn't consistent. It does appear here and there, but there is no gradual buildup of oppression and darkness the further the trip goes. There are moments when it's unclear what is going on. Some transitions are very abrupt.
That said, it paints a very good portrait of many issues: race and clash of cultures, megalomania and cult of personality, and isolation, to name a few. It's a great book, but it just lacks a little something to make me enjoy it more than a simple "like".