Cd-roms seem to be one of the futures that haven’t happened, along with personal jet packs, useful nuclear fission and the new world order. Five years ago, they were going to change the way we thought, render books obsolete and make fortunes for everyone who got into them. Quite a lot of the CD-Roms that were published then are still stranded on the shelves of my local bookshop. Many of the big media companies that piled into the market are now withdrawing. Hardly anyone is making a profit, except Dorling Kindersley, a London-based company; and even Dorling Kindersley has seen its share price drop by half this year. News International has just cut back sharply on its new media efforts; and Time Warner is expected to do the same.

So what went wrong? One explanation is that most of the unsold CD-Roms are rubbish. They do what videos do, only not as well, more expensively and using cranky equipment. This does not only apply to such titles as The Joy of Sex. Today, a good modern computer will display an impressive video in a window on the screen about a quarter the size of a television and costing four times as much. But two or three years ago, when the market was meant to take off, the video available was hideous: the picture looked as if it were constructed by shuffling Lego bricks in front of your eyes.

Few people knew about this because it was quite hard to buy a player for CD-Roms then, whereas nowadays it is virtually impossible to buy a computer without a CD-Rom drive. But this raises a fresh difficulty for the market: the CD-Rom drive will come with nine or ten CDs, and eight or nine of these will be very bad. It is as if every house you bought came with a free bookshelf, filled with the sort of books you can find at Ikea.

The second factor is the internet. Although it delivers stuff of a technically lower standard than CD-Roms, it is is cheaper, more interactive and boundless. No one is making money out of internet content yet, but the big companies which are pouring money in haven’t noticed this.

But the hype was not completely unjustified. There are three or four CD-Roms that no writer should be without. The most obvious is the Oxford English Dictionary, now reduced to around ?250. This is not just a great deal cheaper than the 20-volume edition and a great deal more wieldy than the one-volume miniaturised edition that book clubs give away. It is better than both. You can find things with it that are impossible to discover in the full version. This is fun if you simply want to know all the words from the Aztec language in English, and useful if you want to flatter writers. “Did you know you are quoted five times in the OED, once for illustrating the use of ‘fuck’?” is a question to soften the heart of the most suspicious interview subject.

Unhappily for the industry, the OED achieves all this without any multimedia aspect at all. There is no video; there are no sounds; and even the interface is irritatingly old-fashioned. A similar problem afflicts encyclopaedias. The one worth having remains Britannica, which you cannot afford on CD-Rom any more than you can on paper.

The useful CD-Rom that comes with your computer will be the one that has all the software on it. This distribution of ordinary boring software is the real motor behind the appearance of CD-Rom drives, even on portables, where it adds greatly to the bulk and power consumption.

Andreas Whittam Smith, the founding editor of the Independent, set up Notting Hill CD-Roms after he was ousted from the paper. This was typical of the hopeful wave of new media companies: it produced disks on wine, singing and athletics; all of them aimed at the coffee-table book market. None sold. What was an outstanding success, he says, was their CD-Rom on evolution, produced with Richard Dawkins. This is partly because it was part of the booming popular science market. It was also tied into a name that sells, and, he says, it contained an element of interactivity: it included a slick version of Dawkins’s biomorph programme, which allowed the reader to direct the evolution of insect-like creatures on screen.

But for the most part, he says, the consumer market has just failed to arrive. Although multimedia has many of the production values of film, it has no blockbusters to redeem the costs of all the failures. Here, as elsewhere, Microsoft can appear villainous. “Microsoft has cut the legs off most medium-sized firms by tremendous price cutting,” says Whittam Smith.

Perhaps the proportion of worthwhile CD-Roms is about the same as the proportion of worthwhile books published. But the difference is that you can browse books before buying them. You do not have to commit ?30 or ?50 on the strength of a good-looking box whose contents remain a mystery and cannot be exchanged.

Only one category of multimedia overcomes all the handicaps of being expensive, impossible to sample and copying what is done better in other media: games. Even games originally given away, such as Doom and Duke Nukem 3D, have made fortunes for their writers, for once you have played the free segment, you are happy to pay extra for the rest in all its gory glory.

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