What inspires that light-bulb moment?

New designs and innovations come along all the time, but just where do they come from? These two authors push contrasting lines in books that carry authority but do not have all the answers.

One problem with both books is that they have been produced by repurposing material that started life elsewhere. John Lienhard's book reflects long experience as a radio broadcaster, although he is a distinguished professor of engineering, while Henry Petroski's relates closely to a lecture series.

Starting afresh might have yielded a more satisfying result - and both books would have been better if they had been 80 pages shorter.

But Petroski's main message deserves notice. He points out that failure is an inherent part of success when it comes to design and innovation, and failure can come in many forms. Some things do not work. Others work well but nobody buys them. Yet others work fine but die out when something better comes along.

Petroski's first chapter, on the many devices that have been developed to allow lecturers to present to an audience, is one that readers of The Times Higher might well enjoy. The problem is simple. Most people cannot write or draw on a vertical surface, especially for a large audience. The solutions have evolved over time, progressing from the oil-lit magic lantern to the slide projector, the overhead projector and now PowerPoint.

Other cases he studies include the displacement of gauze by Band-Aid type bandages and the arrival of balloon catheters in surgery to replace big incisions.

However, Petroski's real interest is in bridges and buildings. He writes about bridges in an especially interesting way. He is puzzled that box-girder bridges are still being built after their long history of failure. By contrast, bridge design in general has been good at learning from its mistakes.

As one might expect, Petroski has a wide range of material to draw on in his advocacy of failure as a positive influence. But Lienhard casts his net even more widely. He starts with Otzi, the dead man found in the Alpine ice in 1991, about 5,300 years after he died there. Lienhard makes the point that Otzi was no primitive. He showed signs of being rooted in a sophisticated society that had weapons and tools that used stone and metal in a precise way.

Ötzi is the start of a long account of many of the most important innovations in history, with the overall message that things need not have turned out the way they did. The ancient Greeks nearly had the steam engine, and plenty of people planned air services before the Wright brothers flew the first aeroplane. The stories Lienhard tells are long ones because, as he says, nothing is invented and perfected at the same time.

His real enthusiasm, perhaps, is the history of printing, type and book illustration. He writes eloquently about the emergence of this technology and the new possibilities it opened for learning and empowerment.

His account does contain some oddities such as a mention of "Wiltshire Abbey" (he means Malmesbury), and the assertion that "steam boils". But it has the advantage of looking beyond the few heroic figures who grab all the credit in normal accounts of invention. This level of texture means that his version of events is vastly more informative than alternative renditions.

Innovation today is moving detectably faster than ever before. Apart from some remarks from Petroski on Nasa, neither author looks at high technology. An analysis by Lienhard of how the modern aircraft or computer industries have developed would have added immense value to his book.

In addition, neither author addresses the modern world of big science. Petroski writes about the lack of corporate memory in bodies such as Nasa, which he blames for failures such as the Challenger and Columbia space shuttle disasters. But neither author considers a world where big teams in research universities produce most of our new knowledge, and where innovation is driven by the need for large organisations to keep growing, by developing new products or swallowing smaller firms that have good ideas. Nor do they address the increasing consideration being given to the ethical duties of engineers and scientists. Might a more ethical approach to innovation slow things down by making practitioners more conservative? Or might the result be more thoughtful inventors producing things to meet genuine social need?

Politicians and executives regard innovation as the high road to economic growth and company profit. But nobody really knows how to make societies more innovative or how to ensure that the right innovations appear, as debates across the world show. Both of these interesting books would have been better still if they had paid attention to these issues.

Martin Ince is contributing editor, The Times Higher .