Looking to build on the Stateside success of their 1993 hit "Creep," the band did the only thing they could: make a great — and inaccessible — new LP

At this moment, Thom Yorke looks like the happiest man in rock & roll.

Radiohead’s majordomo is minutes away from his band’s debut on the Late Show With David Letterman. Perched on the edge of a couch in Letterman’s green room, the diminutive, 29-year-old Yorke is vigorously playing air drums to the Warren Zevon chestnut ”Werewolves of London,” which Letterman’s house band (led tonight by Zevon) is vamping on. Grinning impishly — he looks like he’s just itching to shout ”AAAOOOOWWW-WWOOOOOO!” — Yorke pounds his invisible kit with the gleeful intensity of a beat-happy kid. Can this be the same guy who’s currently in contention for the title of Rock’s Premier Tormented Pre-millennial Genius?

The other members of Radiohead — guitarists Jonny Greenwood, 28, and Ed O’Brien, 29; bassist Colin Greenwood, 28; and drummer Phil Selway, 30 — are noticeably less animated. Selway and Colin Greenwood jointly peruse a British music magazine with Radiohead on the cover, while the guitarists amble about the room distractedly. In a few moments, Radiohead will perform a riveting version of their new single, ”Karma Police,” an eerie, almost baroque ballad. The lyrics, delivered by Yorke in his trademark helium whine, seem to serve notice that Radiohead are not just another band of Brit-pop blokes to casually tune in or out: ”This is what you get when you mess with us … ”

Those who know Radiohead only from ”Creep,” their 1993 hymn to low self-esteem, or from the U2-ish big-guitar rock of their second album, 1995’s The Bends, are going to need to readjust their preconceptions. The band’s latest album, OK Computer, features some of the most challenging, least commercial music Radiohead have ever made. The first single, ”Paranoid Android,” for instance, was a six-and-a-half-minute mini-suite that strikes an uneasy balance between bedlam and calm, and lacks an easily identifiable hook. Yet OK Computer has drawn the sort of accolades most bands have to hire flacks to write.

And it’s not only rock critics who’ve fallen under the spell of Radiohead’s sometimes beautiful, sometimes discordant tone poems. Michael Stipe, who’s been a fan since Radiohead toured with R.E.M. in 1995, has called the band ”so good it scares me”; Alanis Morissette requested that they open for her on her 1996 tour; and the East and West Coast dates of their recently concluded American tour were veritable celebrity magnets, attracting, among others, Courtney Love, Sheryl Crow, Bono, Madonna, Liv Tyler, Sandra Bullock, Steven Dorff, Claire Danes, and Calvin Klein.

Like R.E.M. in 1987, or Smashing Pumpkins in 1992, the Oxford, England-based Radiohead, which formed in the mid-’80s as On a Friday, seem to be on the brink of cracking the mainstream. Naysayers may carp that the band is going about it all wrong; after all, didn’t R.E.M. and the Pumpkins get more accessible over time? Still, judging from the 4,000 or so worshipful fans who recently packed Manhattan’s Hammerstein Ballroom on the last date of Radiohead’s American tour, relishing every stray bit of feedback or vocal nuance, a Radiohead show is a near-religious experience. On such devotion are empires built.