If you read this as strictly a work of fiction, it's clearly excellent. The use of language, the characterization, and the building of tension are all very strong. But this isn't strictly a work of fiction, so my reading of it is complicated. I'm not sure if this is true of journalism, but doing this kind of research in an academic setting would require a certain amount of ethical clearance, and I honestly think that's a good thing because it ensures that the participants are treated with respect and dignity. Based on my reading, it seems that Capote paid his way into the good graces of some of his interviewees or folks who could put him in contact with interviewees. He made promises to folks that he didn't keep. He mischaracterized people and in some cases entirely made up conversations and events that didn't actually happen. With this in mind, it's hard not to read this as a bit of an ego project, like it's Capote spitting in the face of ethical research or good practice and instead just actively trying to win a Pulitzer (I guess he was outspoken about his disappointment about this book not winning).
The writing was good, but I did feel like toward the middle/end it started to get rather redundant and long-winded. It wasn't a surprise what the outcome would be at all, so the focus on the trial wasn't all that interesting to me.
This also plays out the same way every murderer story plays out when you tell their backstory: they are victims of a traumatic history who have experienced very little empathy in their lives and therefore have no empathy for others. Does it justify their actions? Of course not, but society will continue to produce people like this for as long as we continue to treat people in this manner. We reap what we sow.
It is terrible that the Clutter family died under such tragic circumstances, and maybe their story deserved a better handling than Capote gave it, but as Capote pointed out, for every Clutter family, there were ten others no one had even heard about.
