Even though the author is a troglodytic paleoconservative (both anti-egalitarian and anti-libertarian), the text itself is a masterwork. This volume contains 400+ pages of supplementals, including textual criticism, contemporary reception, other writings by the author regarding the arts, plenty of historical data about the Congo, 19th century writings on race, and several hundred pages of literary criticism, all very insightful. There's even a few essays on the relationship between the novella and Coppola's film. It may lack in some areas regarding literary criticism, with more discussion of recent cultural theory developments (race & gender politics) than I needed--I'd've appreciated some samples of criticism from the first half of the 20th century--the items that the second half accuses, rightly it seems, of ignoring the race politics of the text (We are given to understand that the earlier criticism ignores this because there are a fair amount of analyses of that period in the later 20th century writings contained herein, which also means that the earlier period is not entirely absent.)
The novel itself is laden with subtlety and complexity, which seemed to have been missed by many reviewers; much of this is drawn out by the critical essays included with the text, particularly the pieces by Watt, Brooks, and Erdinast-Vulcan. (The included leftist writings on race, gender, and empire are all great, too, of course.)
Probably the recommended edition for this text, which is, apparently, the most taught item of its length in English. That in itself suggests that it should be taken very seriously by all literate persons.