Pop's a fickle business. One minute you're playing to an audience of 10 in a friend's living room, the next you're picking up prizes at the music industry's most glittering office party.

While few could claim to be surprised at Franz Ferdinand, the Glasgow band led by the singer Alex Kapranos, picking up two prizes at the Brit Awards this week - if The Darkness dominated 2003, it's safe to say that Franz Ferdinand owned 2004 - one would be forgiven for being a little startled at the speed of their ascent. In their 18-month career, the band sold two million copies of their debut album and became the most successful British act in America since Coldplay. Their popularity appears contagious too.

Whenever the singer Alex Kapranos speaks out in praise of a band, their stock immediately goes up. Kaiser Chiefs and Bloc Party are among those to have been taken under his wing in the past year; now both bands are well on their way to finding mainstream success.

Named after the Austro-Hungarian royal whose assassination was the catalyst for the First World War, Franz Ferdinand are the product of a vibrant Glasgow art scene. (Their first show was at an art exhibition held at their friend Celia Hempton's flat.) Along with Kapranos, the group comprises a failed judo champion (Paul Murphy), a painter of fine art (Bob Hardy) and a Blackpool-born graduate of the Munich Conservatoire (Nick McCarthy).

Forming a band, the singer has said, was "a bit of a laugh", an idea that came to him when he inherited a bass guitar from Mike Cooke of Scots troubadors Belle & Sebastian. Nowadays, however, music is a serious business for Kapranos. He is meticulous about how the band should sound and be presented. Rules include no guitar or drum solos, no chords (just notes) and looking at the audience straight in the eye.

There's nothing especially original about the singer or his sound. Kapranos's nifty haircut and penchant for skinny ties hark back to the late-Seventies/early Eighties new wave bands (this is a man who wouldn't be seen dead in a pair of jeans) while his music is similarly backward-looking, prompting comparisons with Joy Division, Sparks, The Fall and Talking Heads.

Like Talking Heads' David Byrne, Kapranos is as interested in art and literature as music and wears his intellect on his sleeve. In interviews he is more likely to be found discussing the influence of Russian constructivist art on the band's record sleeves than who he's dating. Where Oasis' Noel Gallagher once bragged about having only read one book in his life, Kapranos, by contrast, is a big reader and claims to owe his biggest debt to the Soviet-era magical realist author Mikhael Bulgakov. Franz Ferdinand are also possibly the first band in rock history have started their own book club on tour.

That's not to suggest that a high IQ in pop equals instant popularity. Radiohead's political high-mindedness saw them derided by their detractors as elitist nerds, while Coldplay's interest in FairTrade has turned them into dull do-gooders. Even Morrissey, whose songwriting with The Smiths owed a huge debt to his literary heroes, from Shelagh Delaney to Keats, seems to have shed his literary affectations in recent years.

But Kapranos has been clever about his cleverness. He's careful not to get above himself, and his public pronouncements have stayed by and large within the realms of music. Last month, following in the footsteps of Stephen Hawking, Seamus Heaney, Mikhail Gorbachev and Zaha Hadid, he delivered a speech at the prestigious Edinburgh Lectures in which he called for state support of rock music, suggesting bursaries should go to bands as well as orchestras.

But the real key to Kapranos's success is that he never underestimates the intelligence of his audience. He has quipped about his music being somewhere between Joy Division and a boy band, and it's not far from the truth. The Franz Ferdinand sound marries art-rock with pop and provides fodder for the brain and the feet. It's not surprising that just two years into their careers, the band's admirers are as diverse as they are numerous. Chanel used their music to promote its last collection while Dior wanted the band to wear its clothes on tour.

Tony Blair recently pronounced himself a fan, to which the singer responded, "I guess that puts us up there with King Crimson." It's testament to Kapranos's shrewdness as a businessman that he chose to sign a deal with the small but highly credible independent label Domino. He said he was won over partly through the label's hip roster but also because, rather than try to impress him with a fancy restaurant, the owner Laurence Bell cooked them dinner at his home instead.

By September 2003, following the release of their debut single "Darts of Pleasure", the music press was hailing Franz Ferdinand as the saviours of rock. Four months later, their second single "Take Me Out" had shot straight into the charts at No.3 and Time and Le Monde were begging to interview them.

The real turning point came, however, when Franz Ferdinand won the Mercury Music Prize last year, beating Keane, Basement Jaxx and The Streets. Unlike the Brits, which reward sales, the Mercury is by far the most credible award in the music industry calendar.

Kapranos's full name is Alexander Paul Kapranos Huntley, though three years ago he decided to drop Huntley. One of three children, he spent the early part of his childhood in Sunderland, though the family moved to Glasgow when he was 14. He was, by his own admission, a weedy child who disliked sport and was prone to bouts of asthma. He began writing songs when he was 15 despite the fact that his piano teacher had told his parents that he was musically inept.

Kapranos began his university career in Aberdeen studying divinity, but he left six months in and enrolled at Glasgow to read English. Throughout his 20s, he did a variety of jobs which included washing dishes at a restaurant, booking bands at a local venue and teaching English and information technology to asylum-seekers in Glasgow. Long before he was famous, he drove a Land Rover across Kosovo for an anti-landmine charity.

In early interviews Kapranos revealed modest ambitions - the band's only aim, he said, was to "make music for girls to dance to", though there's a lurking self-confidence in his lyrics. The song "Dark of the Matinee" has him chatting to Terry Wogan on TV, while in "Shopping for Blood" he declares himself "the new Scottish gentry".

His caginess about his age - he has been known to tell journalists he is 28 though, in fact, he is 32 - could be written off as vanity, although a more likely explanation is Kapranos's awareness of the music industry and its wiles. You'd be hard pushed to find an up-and-coming male artist over the age of 30, while women are generally considered over the hill at 25.

So what next for Kapranos? It's unlikely we'll see him tripping down Hollywood's red carpets with a celebrity wife in tow a la Chris Martin. His current beau is Eleanor Friedberger from the eccentric indie four- piece The Fiery Furnaces.

Critical to his future is the next album. His ascent from would-be musician playing to his pals to entertaining crowds of thousands has happened with ease, though expectations surrounding the next LP are high. The Strokes, to whom Franz Ferdinand have been frequently compared, were casualties of their own hype when it came to their second album, as were the Stone Roses 10 years ago.

"It's exciting to be at this stage, where you've established a certain sound and a particular attitude, but you plan to do something a bit different and move on," he says. "I don't understand why more bands don't rise to that challenge." You have to admire his confidence, though some might say that it's easier said than done.