You might thus assume that superhero comics, the original properties on which these franchises are built, are in flush times. They aren’t. The upper limit on sales of a superhero comic book these days is about 230,000; just two or three series routinely break into six digits. Twenty years ago, during the comic industry’s brief Dutch-tulip phase, hot issues of “Spider-Man” and “X-Men” sold millions.

Where this audience went is a bit of a puzzle, especially because comics, broadly speaking, are respectable as never before. Good cartoonists’ books are reviewed in the quality papers and nestled on readers’ shelves next to comic-book-inspired novels by Michael Chabon and Jonathan Lethem. Even the University of Chicago, where fun goes to die, recently held a three-day conference to which it invited brilliant cartoonists like Chris Ware and Daniel Clowes.

If no cultural barrier prevents a public that clearly loves its superheroes from picking up a new “Avengers” comic, why don’t more people do so? The main reasons are obvious: It is for sale not in a real bookstore but in a specialty shop, and it is clumsily drawn, poorly written and incomprehensible to anyone not steeped in years of arcane mythology.