Most book writers like to start at the beginning. It is, after all, a very good place to start. (Thanks, Maria.) However, like many aspects of writing a book, working out where to begin isn't always as simple as it seems.
First-time authors often get stuck at the introduction. Until they have to write one themselves, most rookie book writers have never considered that introductions ain't introductions. Some books have an introduction, but others have a preface, some a foreword and others still a prologue.
What's the difference?
The following are more conventions than strict definitions, but here are the descriptions I use for each of these possible 'beginnings'.
Foreword (not forward!)
The foreword (think fore-word) is typically a short introduction to your book written by someone else. Ideally that someone else will be someone well known: an established author in their own right, an expert on your book's topic or someone who can add serious cred through their association with you. Their job is to briefly explain what a great person you are and why your book should be read.
If you find someone more famous than yourself to write you a foreword, you might put their name on the cover the book to give it extra gravitas. Have a look on your bookshelf and you'll find an example of what I mean – "Foreword by..." – usually under the author's name and in a smaller font.
A preface is something you would write yourself that explains the background of your book, as opposed to introducing its content. It might explain your motivation for writing the book, something of your background that qualifies you to write this book, or indeed why this book is necessary at all – its 'point of difference' to use the marketing vernacular.
In a business book, the preface can be a good opportunity to establish your credibility with the reader. But don't go on – keep it to no more than three pages, preferably less.
The traditional introduction is an introduction to the content of your book. You will normally use it to set up a context for the material your book is going to cover, and perhaps outline briefly each section or chapter. Particularly in business books, which may not always be read from start to finish, this sort of outline can help the reader find something particular that they are looking for.
Introductions can be a bit longer than forewords and prefaces. My philosophy on them is that an introduction should stand on its own – the reader should not 'miss out' if they choose to skip past it.
Introductions are also best written with a marketing mindset. Many potential readers, picking up your book in a store or downloading an ebook sample, will read the introduction to try to understand whether it will be worth their while buying your book. So make your introduction snappy and engaging!
Prologues are not generally used in non-fiction, particularly business non-fiction. In fiction a prologue, if used, typically provides some background before the story starts. Remember the scrolling text at the start of Star Wars? That's a prologue.
Do I need any of these?
None of these is essential, and there is a school of thought that in today's 'get to the point' world they just get in the way. However, in a business book, to skip any form of introduction is to miss a very good opportunity to position and market your book.
You certainly don't need all of them. I would tend to skip the foreword unless you have someone high profile who can write it for you, or a genuine expert who is perhaps less well known but who can spruik your prowess. Similarly, include a preface if it will add something to the reader's understanding of why this book is needed. If not, skip it and go straight to an introduction.
When to write it?
One last thing about introductions in all these forms: You don't need to write them at the start. In fact it often makes sense not to. Many writers like to draft an introduction at the outset as a way of outlining their book for themselves. If you want to do that, fine. But treat that as something that will probably be discarded at the end. Then, when your book is finished, write a new introduction and/or preface with the final manuscript in front of you. Obviously it makes sense that a foreword would also be prepared only when your foreword writer is able to read something close the final manuscript.