Published 1977 (re-edition 2012).
"Heinlein is a writer who represents a certain strain in our culture, a kind of secular Calvinist vision of the world of the elect and the damned.”
From “The Classics Years of Robert A. Heinlein” by George Edgar Slusser
“Heinlein rarely discussed his own stories at all except in shoptalk with another writer – but he made an exception here. In response to a question about “Coventry” and the “Calvinist” reading that had been advanced by George Edgar Slusser, he hardly needed to think about the problem. Stover and Slusser were both mistaken: they had taken different gambits written into the story that misdirected their thinking.”
From “Robert A. Heinlein: In Dialogue with His Century: 1948-1988. The Man Who Learned Better” by William H. Patterson, Jr.
I was not convinced by Slusser's circular arguments. What I needed was a balanced and objective view, one that would put Heinlein's strengths and many weaknesses into a rounded view, namely is supposed Calvinism. I did not find it here. Philip K. Dick was the only writer to “suffer” a Calvinistic canonization, where every word he ever wrote seemed (seems?) to be treated as sacred writ (e.g., his religious visions are still taken seriously in this day and age). As for Heinlein, I still think the so-called solipsism of his latter novels is much more pronounced than his supposed TULIP-Calvinism.