Harriet Swain finds extras are no longer optional for business books. If your text doesn't come with DVDs, CDs and podcasts, it won't cut it in the student market.

If you know anything about business, you will know that writing a business studies textbook these days rarely makes much business sense.

Yes, there are people who do very well out of it - Gerry Johnson, professor of strategic management at Strathclyde University, for example, was a top earner in a Times Higher survey of academic earners from publishing (January ). But it is a small band, and one that is ever harder to break into.

It is no longer enough to write a book, sit back and wait for the royalties. You also need to supply the accompanying teaching notes, CD, DVD, website, podcast - everything but the T-shirt. It is a big deal for a publisher to commit the outlay this involves to a product or author untested in the market, and on the whole they do not.

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John Saunders, head of Aston University Business School and author of Principles of Marketing , says it is worth writing a textbook only if you have a good publisher behind you, and you will not get a publisher's backing unless you have a solid research reputation or come from an institution that does. "But people with names in the profession are less likely to spend their time writing a textbook because the real acclaim comes out of academic publications," he says.

The demand for extra material is increasing for textbooks in all subjects, but in business studies, this is especially so. Richard Whittington, professor of strategic management at the Said Business School in Oxford and co-author with Johnson and Kevan Scholes of Exploring Corporate Strategy , says: "Students are vocational, time-pressured and businesslike. They are looking for a package, not just a book to read."

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Whittington says a book is relatively easy to write, but an author or group of authors must invest a lot of time keeping it up to date. His team publishes new editions every three years and updates the text between editions. This year, for example, it is launching podcasts and a new website. "It's a business," he says. "It's not a book in the old sense."

It is not only students who are demanding more. Lecturers expect added value too, says Jo Barber, marketing manager for Pearson Education. She says that as they become weighed down with administrative duties, they expect more supplementary teaching material. They are also looking for resources that will help them manage students from increasingly diverse academic backgrounds, that will offer something for beginners while stretching the more able. And they increasingly expect to find resources online.

Readers expect websites to be constantly updated, but even when it comes to books, authors cannot afford to let their texts fall too far behind the times. The second-hand textbook market, already strong in the US, is becoming increasingly dominant in the UK. To persuade indebted students to buy a new book, it has to offer something that is genuinely new.

Win Hornby, a teaching fellow at Aberdeen University Business School, says the more diverse student population has also led to greater emphasis on contemporary events and references to news stories related to what they are studying. "You cannot have the same expectations about them reading great chunks of academic textbooks to get through the course," he says.

Added to this, the business world itself is moving faster than ever, according to Cary Cooper, professor of organisational psychology and health at Lancaster University. He says developments such as outsourcing, managing people remotely, short-term contracts, work-life balance and downsizing are transforming the way business studies is taught year by year. Case studies rarely stay relevant for more than two years, he says.

And students like case studies. With business students being more international than most, books need to draw on examples from the range of countries represented by their students. They also have to appeal to the typical student. Saga does not make for a good business case study, whereas the iPod does, Saunders says. And case studies can mean different things according to the country. "In France, we mention McDonald's in the context of ethics," he says. "In America, it's a burger."

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This has become an important issue because the number of successful texts has not just become concentrated within the UK but across the world, with several turning into global brands. "The concept of a British textbook is rather silly in a business context because no one does business in little old England," Saunders says.

In addition to the standard global brands, there is also increasing fragmentation of the field into specialisms, with numerous texts on marketing, for example.

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Pressure to specialise comes from two directions. First, authors who specialise in other disciplines can profit from the popularity of business studies. Even John Sloman, whose Essentials of Economics has dominated booklists in economics for many years, has produced a business economics book. Then, as the business world becomes more complex, fewer authors feel they have a broad enough knowledge to attempt a general text.

There is also the increasing trend for bite-sized texts, shrunk to fit shorter modularised courses. And students are increasingly set chapters of books rather than whole volumes, as many of these are available free of charge online.

Journal articles are also an increasingly popular feature of student booklists because they are so easy to access over the web, Saunders says.

They fulfil the demand to be up to date, and both globalised and locally relevant.

But textbooks are still vital since they provide a framework for the confusing mass of material that today's students face. However, where they do feature on student booklists, they are precious, carefully selected tomes to be treasured. "The tendency now isn't to have great long booklists but to focus on one or two essentials," Hornby says. Students don't go and buy a lot of these things now. They're too expensive."

Barber says there remain opportunities for new textbook authors in up-and-coming areas. But business studies experts would probably see greater returns from sticking to an article eligible for the research assessment exercise rather than entering the draining multimedia world of business studies textbooks.

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