The Whole Internet has sold more than 300,000 copies and is high on the list of bestselling computer books in Britain and in the US.
He attributes his success partly to timing: when the book was first published nearly two years ago, little else was available to the rapidly growing numbers of Internet users.
Undoubtedly, the Internet is the media phenomenon of the Nineties. Up to 30 million people are using it, and at least a million more are signing up every month.
What is driving this phenomenal growth? Mr Krol thinks it is partly urban professional peer pressure. 'It's more than a hi-tech toy,' he says. 'Everyone is talking about and writing about the Internet, and some people are starting to feel inadequate if they don't have an e-mail address on their business cards.'
Many newcomers wrongly perceive the Internet as just another e-mail system. Mr Krol has a curiously romantic vision of the system: he compares its users with 18th-century travellers seeking food and shelter in houses they reach at nightfall. As they do not abuse the hospitality provided, neither should Internet 'citizens' be greedy with the network's resources. He cherishes its informality and lack of restraints, and constantly refers to the Internet tradition of sharing information and resources.
A succession of technological stimuli, mostly developments in finding and retrieving information, have helped the Internet to grow. One milestone was the launch of the World Wide Web (WWW), an attempt to organise all the information on the Internet as a set of hypertext documents. A piece of software called a 'browser' is required to read the information. Mosaic, currently the most popular version, is a 'graphical browser' that enables Windows or Macintosh devotees to use the WWW.
There is still much room for improvement on the Internet. Many information sources are poorly organised, and WWW is no exception. Mr Krol's critique focuses mainly on those pages that seem to be constructed solely around other references or links. Just fine if you want to 'surf' the Internet, logging on to servers throughout the world for the hell of it. But if it is information you need, reading a 1,000-word piece containing 100 cross-references is not the best way of obtaining it.
Mr Krol's greatest fear is that the telephone companies consider Internet a great opportunity to charge users more; once they start charging by distance or time or volume of data, the operation will fall apart. And the US government says it will not continue to fund Internet for ever. When subsidies are phased out, money will have to be found to keep it going. But metering might not be all bad: charging users would weed out those not prepared to pay a minimal fee, and would fund further development of the infrastructure.
Commercial charging would hurt the universities most, Mr Krol believes. 'A lot of universities with big, fat connections are going to have to pay their own freight,' he says. 'That's causing a dilemma, because they are already addicted but they don't know where the money will come from.'
Much of the universities' Internet usage is recreational rather than educational or academic. In 1975, Mr Krol spent his lunch breaks at the University of Illinois in Urbana playing what he describes as a primitive version of a Star Trek game. Through the ARPAnet, the first version of the Internet, he would log on to a computer at Stanford Linear Accelerator Laboratory in California. And today he still sees games as a great way of educating people in Internet technology. He does not know what proportion of university usage of Internet involves games, but says that students spend hours discussing sex on bulletin boards and forums, or e-mailing former high school friends at colleges in different parts of the country.
Professional people use Internet primarily for business. Some companies worry that if they give all their employees an Internet connection no work will be done, although Mr Krol feels that such fears are misplaced.
Mr Krol dismisses concerns about 'cyberpornography' which obsess so many journalists. If people want to look at grainy images scanned from photographs printed in widely available magazines, he argues, why stop them? His university's only policy on such material relates solely to issues of copyright.
Mr Krol is uncertain where the Internet will be in five years' time, but is optimistic that as the telephone companies start linking up homes with fibre optic cable, new applications will arise to take advantage of the extra capacity.
'The Whole Internet', Ed Krol, published by O'Reilly, pounds 18.95