One of the great things about writing a business book is having the time and space to explore an issue properly. You have something you want to say, or an experience you want to share, and a book allows you to do this in a way that feels 'complete'. It allows you to present a well-rounded argument.
If you're being honest with your readers, your case will be built on a solid foundation of evidence. You won't present an ideological view that you then back up with evidence that supports your case, no matter how tenuous, while conveniently ignoring anything to the contrary. That is the domain of neoliberals, climate change deniers and anti-vaxxers.
Rather, you will use real evidence. But what is 'real' evidence?
In the context of a business book, as opposed to an academic dissertation, there are two main forms of evidence.
Your own experience, case studies and research
Obviously the most powerful and original material you can share is that you have collected yourself. Case studies of real-life situations you've been through can be particularly useful to others in similar situations. Even more so if you have a number of similar situations in which similar actions have been taken and similar results achieved.
The standards of evidence in a business book are rarely as high as they would be for an academic paper, in terms of strict sample sizes and repeatability. Nevertheless, if you want to be taken seriously it is good to be able to provide quantifiable results linked to specific initiatives. A sample size of one will never have a lot of credibility. Nor will assumptions and generalisations.
Others' experiences, case studies and research
No matter how much experience you build up you'll never be able to 'do it all'. There will always be things to learn from others. And of course, as an expert in your area, there will be external sources you're aware of that your readers may not know about. So there's nothing wrong with citing other information in your book.
However, this should be done responsibly – at least if your aim is to be honest. This means doing more than a quick Google search, grabbing a few statistics that appear to support your argument and then quoting those numbers – even if you reference the sources.
For a start, especially in business, a very large number of so-called studies are anything but. Dig just a little beneath the surface and you'll find that most of the statistics floating around the web are based on self-serving surveys conducted by individual firms with a product to sell. Unsurprisingly, these statistics always seem to support the use of said firm's services.
If you're going to quote statistics, or any other external evidence, make sure you find your way back to the primary source (i.e. not the article quoting the evidence but to the original source of that evidence) and verify its impartiality. In business, two of the best sources are outlets like Harvard Business Review and McKinsey Quarterly but there are plenty of others.
Of course, there is nothing to stop you saying whatever you like in your book and using as much evidence of ill-repute as you like. You can completely make stuff up if you want to. Plenty of people do this all the time and get away with it. Much of the supplements industry comes to mind. My hope is that that is not what you are interested in doing.
As usual, if you have any questions or comments, please add a comment below or contact me.