With Kafka, we got great novels out of the postumous publication. The publication of Joyce's letters to Nora Barnacle, however, paint him as someone who "[fastens] intently on peculiarities of sexual behaviour, some of which might be technically called perverse"[1]. No one has really benefited from their publication, except perhaps gossip columns.

I think I would stick to the author's desires. As great as Kafka's work is, I don't think we are "entitled" to them. But I can understand the opposing point too.

[1] Richard Ellmann, Selected Letters of James Joyce, Introduction, Faber & Faber, London, 1975