It's funny, this thing about roads - how, beyond a certain length, they begin to take on a life of their own. Before you know it, people are hopping into cars and buses and setting off from one end to the other, not to get from A to B, but to show that road who's boss.

Which is why Calder's book makes a pleasant change. Sure, he could have set off from Alaska and, 15,000 miles later, pitched up at the Straits of Magellan bursting to tell us how he travelled the entire length of the world's mightiest road.

But instead, he begins down Mexico way and pootles along that section of the highway that is, to all intents and purposes, Central America's main street. And at the end of it all, when he types up his notes, it's not to show us what a great adventure he had but to persuade us to try it for ourselves.

Okay, so Central America's not all plain sailing, but you couldn't wish for a more detailed survival kit. From maps and jabs to buying cigarette papers in Costa Rica, Calder has thought of everything.