Locked away in the back room of a library at Princeton University in New Jersey, available for entry only to those who apply with two forms of ID and agree to be supervised by a custodian while reading, there is a small book.

In that small book, there's a short story: The Ocean Full of Bowling Balls, a standalone prequel to J.D. Salinger's sole novel, Catcher in the Rye, that explains its protagonist's muddled, often misunderstood motivations. And behind that story — behind the reason it is to remain strictly guarded and unpublished until 50 years after Salinger's death — is a fear.

The fear, expressed both by the famously reclusive author and his son, was that Salinger's fame would overshadow his work — or that it already had. The fear was that his writing had grown so popular it was impossible to judge his stories on their own merits. And that his fans' interpretation of, and obsession with, his writing had somehow robbed him of it.

"When you publish, the world thinks you owe something," Salinger, who died in 2010, said in his last interview. "If you don't publish, they don't know what you're doing. You can keep it for yourself."

It's a fear that Joker: Folie à Deux director Todd Phillips was no doubt guided by. A follow-up to his Oscar-winning Joker released exactly five years ago — which starred Joaquin Phoenix as a sort of real-world interpretation of the chaotic comic book supervillain — this latest movie is less a sequel than an epilogue. Instead of an independent production, it operates as a coda to a film that sparked debate over a romanticization of incel culture (and necessitated bans against Joker-inspired outfits and police crews posted outside screenings), and is almost completely devoid of a plot of its own.

Bouncing between the Joker's trial for killing five people in the first movie, his courting of fellow inmate and crime-groupie Lee Quinzel (Lady Gaga) and a pack of rabid fans rallying against some social injustice no one seems quite able to articulate, Folie à Deux doesn't bother with consistent character motivations or even a coherent story. Composed almost entirely of flashbacks, it is far more concerned with addressing its own legacy, as Phillips has no doubt lived the hell that Salinger spent the last half of his life feverishly working to avoid.

Unfortunately, Phillips has made something of a misguided mess. We enter and exit narrative blind alleys at will. Plot points from singing prison guards to romance to courtroom drama are introduced and abandoned with all the direction of a free-association exercise. It is nearly impossible to follow, which makes it wholly impossible to care about what is happening to the characters on screen, because this time around, Phillip does not care about their journey.

This movie is in every respect a meta-commentary on what Joker was supposed to mean — simultaneously a more direct and more confusing artistic statement from Phillips that is as disjointed as something pulled from the journal of a narcissistic psychopath. It's a correcting of the record that exists more for its creator than its audience, an unnecessary skin-tag hanging off the original. And, most importantly, it's boring.

Oh, and it's a musical.

To be fair, Folie à Deux might have come out of a noble pursuit. Originally intended as a sort of Watchmen-esque subversion of comic-book hero worship, the original Joker's anti-hero instead swan-dove right into the same unfortunate position as that book's Rorschach: a character made to lampoon the dangerous stupidity of vigilantes, appropriated and celebrated by those it meant to criticize.

Instead of staying quiet like Salinger, Phillips has decided to fight back — while making an admittedly visually beautiful product. In nearly every respect, this Joker undercuts the hero worship, leading to a finale reinterpreting the man posturing as some sort of eternally wronged martyr into something much sadder, more realistic and impossible to misinterpret. By the end, the clown prince of crime is reduced to nothing more than a teenager only able to shrug and scowl when asked what is so woefully unjust about having to do your homework.

It's a fearless spitting-in-the-face of Phillips' fans, who turned the original into the then-highest grossing R-rated movie of all time. Regardless of how bold of a decision, you do not, under any circumstances, gotta hand it to him.

Like Watchmen — or the more recent Bikeriders — Phillips is far from the first writer to take on the task of examining masculinity, only for its targets to miss the mark so masterfully they see overt criticism as endorsement. In fact, making a weird, meta-commentary sequel to those stories has become something of a cottage industry.

Chuck Palahniuk wrote Fight Club 2 as a kaleidoscopic response to misguided fans casting Tyler Durden as anything other than an idiotic, self-involved psychopath. You'd be excused for thinking the Wachowskis released the drastically different Matrix Resurrections specifically to antagonize a subset of their audience. Bryan Lee O'Malley's abstract Scott Pilgrim sequel directly addresses the misreading of its titular character as some aw-shucks everyman.

As far back as the 18th century, Goethe rewrote and released his Sorrows of Young Werther, the novel that made him famous, after its morose, self-indulgent protagonist may have sparked a wave of copycat suicides.

But these works managed to surpass Folie à Deux in actually being entertaining — something Phillips's original Joker, in spite of any thematic issues, also managed. And that's ignoring the misstep of turning this screed into a bad jukebox musical; this from a man who clearly does not watch, understand or respect them.

This is combined with the ill-informed decision by Phoenix and Gaga to record their performances live — a gimmicky strategy that gets media attention but often produces disappointing results, as in Les Mis and Cats (and has already generated self-congratulatory headlines for the upcoming Wicked).

The vocals here are no car crash, but they are nothing to write home about — and further suggest Phillips should've taken Salinger's advice, and kept this whole thing to himself.

Because whatever the message on the meaninglessness of the original and pessimistic middle-finger to the fans who misunderstood it as empowering, Folie à Deux is just not fun to watch. It may one day be appreciated as an experimental genre piece, as some have optimistically predicted for Megalopolis. But creating a film this scattered and impotent, as if the real Joker wrote it, doesn't make sitting through it worth anyone's time.