I read "Heart of Darkness" after watching "Apocalypse Now" and found that far from being a supreme prose stylist, Conrad wrote prose so glutinous that I could barely trudge through it. I read it again after I found out about Chinua Achebe denouncing the book as racist and didn't get the feeling that it was. He portrayed racists but I didn't have the feeling that he was endorsing them. I've never bothered with Christie and never will more from lack of interest than suspicion of racism (shown in your quotes).