Alas, 'twas the only novel Miller completed during his lifetime.
I wrote those bolded words in case I needed to provide my own segue. But as I think Obi Wan said: "There is hope! There is
another one."
Canticle Author Unsung Even In Death
Walter M. Miller Jr.'s ѕυιcιdє Caused Hardly A Ripple.
His Just-published Sequel[##], Though, Has Provoked Interest In His Work.
[....] A best seller can capture the mood of a moment and be forgotten 3 years later, but for a novel to sell 2 million copies over 37 years, which Canticle has done, it has to offer something extraordinary. [....]
Miller was deeply affected by the 55 missions he had flown over Italy in World War II as part of a bomber crew. One of these involved bombing the Monte Cassino monastery, a centuries-old repository of knowledge that was taken over by the Germans as an artillery spotting post. Miller later agonized over his role in the destruction - only the latest the holy site had suffered over the ages - and it probably played a role in his becoming a Catholic for a decade or so after the war. It definitely played a role in the creation of Canticle. 
I don't know much about the author. I wonder what he thought about Vatican II and the changes. I wonder if he kept the faith or abandoned it when it became absurd in the Novus Ordo. I believe he would have hated the Novus Ordo, just based on what I read in his book.
Miller was apparently a
postwar convert to Catholicism. I'm sure that many of us here would prefer to read, about anyone whom we already know abandoned the Faith, that it happened because of
Vatican II. But that would require fitting 1 decade precisely into a period of not quite 2½ decades (i.e.: 1945--
ca. 1970). I've yet to see any biographic article that addresses whether Miller's time as "
Catholic for a decade or so
after the war" was ended by Vatican II, and from what I've read, I infer that the necessary data, even if "out there" in the form of a diary or personal correspondence, ain't gonna be released by his protective family--not no how, not no where--but I have no privileged knowledge.
"Walt was deeply depressed by post-traumatic stress disorder and had been for half a century," says writer Joe Haldeman, who was the closest thing Miller had to a friend in the science-fiction world. "I don't know how many people he felt responsible for killing, but it was a lot." [....]
The one key person in Miller's life was his wife, Anne [×]. Her death 2 years ago shook him.  In an unconventional letter to the local newspaper in Daytona- , the author of one of the greatest modern religious novels made it clear he had left Western religion behind. [....]
Miller's longtime agent, Don Congdon, said Miller was "the only client I never met, although we talked a lot." The writer had completed 60 pages of a Canticle sequel a long time ago but then became blocked. "He couldn't get rid of it - it was basically depression and booze."  In the late '80s, Congdon made a 6-figure book deal off those 60 pages, and Miller rose to the challenge by writing 500 more - nearly 90 percent of the book. [....]  It seems instead that, with the end in sight, Miller lost interest. With his blessing, a deal was worked out with novelist Terry Bisson to complete the book. "I figured it was going to be a mess, because this guy had been fooling around with it for years," Bisson recalled. "But it was almost finished. It was not a mess. He had written 592 pages and outlined in some detail how he wanted the book to end."  Miller just couldn't do it himself. "He mentioned to Congdon that trying to finish this book was like trying to spit through a screen," Bisson said. "I think it was psychological - he felt that when he finished the book that would be the end of him." 
The sequel is said to be
parallel to the 2nd part of the 3 parts of the novel, which were originally written as 3 separate short-stories.
-------
Note +: <
http://articles.orlandosentinel.com/1997-10-09/lifestyle/9710080756_1_canticle-miller-novel>. This article is concluded on a
2nd Web-page linked from the 1st.
Note #: Yes, the nationally famous
Beach (Volusia Co.), at the eastern end of what Central Floridans poëtically refer to as "The I(nterstate)-4 Corridor". Miller had been born (1923) a few miles south, on the other side of "Ponce (de Leé) Inlet", at New Smyrna Beach, now federally bounded on the south by Canaveral National Seashore. The oddly unnamed "local newspaper in Daytona", which published a letter from Miller about the death of his wife, is the
Daytona Beach News-Journal, in case anyone is inclined to try to find that letter (I infer a date
ca. Fall 1995).
Note ##:
Saint Leibowitz and the Wild Horse Woman. I'd be surprised if there weren't CathInfo members who'd be pleased with the opportunity to find & post a link for its purchase.
Note ×: "
Anna Louise
Becker (1945-1995)" per Wikipedia article on Miller. So Walter M. Miller Jr. is
not the writer surnamed Miller who was married to Marilyn Monroe; for that much more famous writer, look up Arthur (no relation as far as I know).