Perhaps the most time-tested, shopworn but reliable pop star subject matter is “How did I get here?” followed by “Will they let me stay?” Megafame is lonely, leaving sensitive souls to ponder whether they’re worthy of all the attention showered upon them. And megafame is distorting, making it hard to assert your identity when the public-facing nature of your work defines you long before you can define yourself.

From that resulting existential uncertainty, Shawn Mendes has made hay. His search — for himself, for love, for approbation, for confidence — has become the most vivid subject of his music. That was true on his self-titled 2018 album — his third full-length, which pulsed with theatrical dolor — and is even more so on his new album, “Wonder,” a maze of occasionally catchy songs about self-doubt and moroseness interspersed with breathless pleas of love.

For Mendes, 22, who doesn’t have a firm musical ideology beyond up-tempo pop-rock, threading his album through with anxiety about the fan-star dynamic and the emptiness it masks becomes an aesthetic position. Lyrics like that are desolate, a little tragic; they necessitate a singing style that’s not overly effusive. “You have a million different faces/But they’ll never understand,” he sings at the beginning of the sweetly ponderous “Intro,” the album opener, rendered with torch-song sorrow. That’s followed by the stomping, stirring title track, the song with the most vigor here. He sounds most alive when in agony: “If I’m being real/do I speak my truth or do I filter how I feel?”

That sort of loneliness recurs throughout this album: “Call My Friends” is about what happens when there’s no room for a partner on fame’s ride, and “Song for No One” is a blurry photocopy of the angsty songs Mendes leaned into on his last album: “I’m all alone/10 missed calls, a couple texts/None of them are who I’m looking for.”

“Wonder” is, overall, much less polished than Mendes’s last album or the one prior, “Illuminate,” released in 2016 and still his best work, which featured oodles of tightly zipped and anxious teen pop-rock. (Though he works with some of the same collaborators, including Kid Harpoon, Nate Mercereau and Scott Harris, notably absent is Teddy Geiger, the songwriter and producer who gave those albums ballast and nerve.) Harry Styles might get the glamorous magazine covers and the thirsty memes, but Mendes in general has been a far more convincing avatar of this approach. Styles’s music suggests a perpetual ambient sonic vision quest, while Mendes at his best has tossed off a series of crisp hits with flourish.

On this album, though, his lyrics meander and stop short of true sentiment, and his rhythmic deliveries feel less cohesive. He still has a way with swell, understanding how to inflate his voice from whimper to peal. But on this inconsistent album, rarely does his singing convey depth of feeling. The handful of dippy love songs — “24 Hours,” which chirps like Christmas music, or the sock-hop-ready “305” — don’t match the mood. The only exception is “Look Up at the Stars,” an ambivalent love song about the relationship between idol and idolizers. “The universe is ours/And I’m not gonna let you down,” Mendes sings tepidly, like someone who understands — and is resigned to — how much of that dynamic is beyond his control.

The most famous male pop star of the last decade is burdened by a similar ambivalence about success. That would be Justin Bieber, who duets with Mendes on “Monster,” a smoky, smooth mope-off, with the two singers performing a kind of gut check for their fans. “You put me on a pedestal and tell me I’m the best,” Mendes sings, without a flicker of joy.

Four years and a couple of lifetimes older than Mendes, Bieber has long been a performer for whom superstardom itself is the raison d’être, with music a distant second (or fifth, or ninth, at least up until this year’s “Changes”). His verse is more tart, more nostril-flare: “Lifting me up, lifting me up, and tearing me down, tearing me down.” He sounds exasperated, over it. An older brother letting his little brother know just how cruel the world can be. He understands he got here, and he’s looking for an exit.

Shawn Mendes
“Wonder”
(Island)