The name of an audio book featured by the weekly podcast This Week in Tech - casually referred to as TWiT - recently grabbed my attention. It was titled Confessions of an Economic Hitman and looked at how highly paid banking professionals help the United States government ensnare poor countries in debt. Until hearing about this, I vaguely assumed all audio books were as boring as nagware. The term 'audio book' made me think of retirees foraging in libraries for greasy cassette copies of Jane Austen novels. Yawn. The impression was cemented by the free audio books in circulation on the internet via worthy, socialist-style public sites. Read by volunteers, most of these audio books have a desperately amateur-night feel - all ponderous enunciation that caters to the slow-and-hard-of-hearing market: 'Curiouser ... and ... curiouser ... said ... Alice.' My answering machine injects more expression than these actors, who read their lines as if they're addicted to Ambien and other drugs used to treat insomnia. The time has come to pay for quality, spoken audio entertainment online. Log on to one of the foremost commercial audio book hubs, Audible.com, and you will find its selection is not cheap. If you are used to downloading free MP3 files, the prices may seem extortionate. Still, you will not find many free audio books doing the rounds using free peer-to-peer file-sharing programs. The likely reason, in terms of megabytes, is that books are usually huge. The ones you can download fast from dedicated servers at sites such as Audible.com, iTunes and AudioBooks-Store.com are worth the outlay. They expand the horizons of mobile sound technology, which has always been spun as a music medium. 'This is the product that will satisfy those young people who want to listen to music all day,' Sony founder Akio Morita said when the Walkman debuted almost 30 years ago. When science-fiction novelist William Gibson first saw the Walkman portable audio player, he was mesmerised and instantly knew he had to have one. Despite being broke, he splashed out. He has not experienced a similar dramatic reaction to an invention since. 'I recognised the revolutionary intimacy of the interface. For the first time, I was able to move my nervous system through a landscape with my choice of soundtrack,' he said. The catch with literary soundtracks is they usually come in neat but obscure formats, encrypted in the interests of digital rights management. Don't even think about trying to convert Audible .aa or iTunes .aac files to MP3s, using the free methods flagged by various pirates online. To succeed in such a subterfuge, you need the imagination of Einstein, the perseverance of Napoleon and the low animal cunning of Rasputin. Which is another way of saying don't bother - you will try all week and end up with no narrative, just noise like a scratchy violin in a gale. You need to have the right kind of digital sound player so you can play the files at the right size from the outset. The respective online book vendors tell you which do the trick. Once you have your book loaded up, it should serve as a wonderful downtime filler and boredom killer. A stroll with an audio book whispering into your ear has to be the easiest and most painless form of exercise you can indulge in. As you continue on autopilot, the calories melt away.