In the two years since their last album, Amnesiac, Radiohead have been dethroned by Coldplay as the kings of serious, pointy-headed British rock. The same fans who made Radiohead one of the world’s biggest, most admired bands after OK Computer in 1997 were bewildered by the free-jazz squalls and dissonant electronica of Kid A and Amnesiac and defected to Coldplay, who sound like Radiohead from before the days when Radiohead could scare your date.

The buildup to their sixth album, Hail to the Thief, suggests that Radiohead want to regain their fans — and their crown. Guitarist Ed O’Brien has claimed that the record “won’t alienate people…I think we’ve got over that musical snobbery. We feel rehungered.” He compared Radiohead’s current “swagger” to that of the Rolling Stones circa 1968. You can almost sense ears pricking up.

But ears are liable to quickly prick down again once they hear the album. Although it’s not as willfully obtuse as Kid A, it’s roughly 87 percent alienation and 13 percent swagger. The most commercial moment may well be the first single, “There There,” which features the rare return of actual guitars, including a charmingly strangulated Jonny Greenwood solo, but it stays strangely subdued until an acceleration well past the four-minute mark. By contrast, OK Computer’s “Paranoid Android” sounds like Van Halen.

Radiohead repeat that pattern throughout this confusing album, offering nothing in the way of a chorus, nothing approaching a hook, nothing graciously pleasing. The songs are packed with nice touches, but they sound vague and half-finished. Thom Yorke’s high, alien voice drawls and croons, often wordlessly, as though he has given up on language.

“Myxomatosis” (named for a highly lethal disease that infects rabbits) isn’t much more than a monstrous, proggy bass-synth riff, and Yorke haltingly declares, “I don’t know why I feel so tongue-tied.” “Backdrifts” offers the same whirring loops found on Amnesiac’s “Like Spinning Plates,” and it has a lovely piano line buried in the mix. “Sit Down, Stand Up” appears to be part of a song. Admittedly, it’s the best part, building slowly from pattering techno beats to speedy, drum-laden anxiety, but the excitement is undercut by a puzzling sense of incompleteness.

Hail to the Thief sounds less like a band swaggering than a band determined to keep circumventing and defacing rock & roll as they savor the outer limits of texture and deliberate inarticulateness. Sometimes they focus on an idea: “Sail to the Moon” is a woozy ballad with Pink Floyd orchestration, testament to how marvelous Yorke sounds when he eases up on the histrionics. “A Punch-up at the Wedding” is presumably the type of song that excited O’Brien — softly funky bass, lambent piano and caustically funny lyrics: “You had to piss on our parade,” Yorke complains, as distraught as ever.

Not the stuff of belly laughs, sure, but it’s a vast improvement on the rest of the mood, which reaches an apotheosis of misery on “We Suck Young Blood.” This is a cartoonist’s caricature of Radiohead: whining, tuneless, agonizingly slow and so depressing you can’t imagine anyone wanting to hear it twice. The song doesn’t exactly jump the shark, but it does walk listlessly around the shark tank, moaning about the appalling conditions marine life endures in captivity, before slumping home in a sulk.

Complaining that Radiohead sound miserable is like complaining that Britney Spears is tacky: That’s the essence of their appeal. Radiohead are meant to carry the weight of the world’s problems on their scrawny shoulders. Nevertheless, there’s something unappealing about Hail to the Thief’s brand of glum. It offers none of the thrilling anger that powered OK Computer. The album seems resigned, defeated, passive — like an hour-long sigh.

Lately, rock bands have seemed so desperate to please that their every move seems to imitate some other successful act, so it’s hard to criticize a group for taking risks. But there’s a world of difference between admiring a record’s ambition and enjoying the results; it’s the difference between Radiohead in 1997 and in 2003.

Hail to the Thief is the third straight Radiohead album that’s difficult to love: It’s too vague, too remote, too encased in its misery. The only concrete point it makes is that the thrilling band that made The Bends and OK Computer has dug its heels into joyless, post-rock dirt, and it’s not coming out.