Which book should you write?

Authors often have more than one possibility in mind for their next nonfiction book. Books require so much effort and mindspace that it’s rarely possible to work on more than one at a time. But how to choose?

In the rest of this post I’ll show you a logical, analytical way to make the choice. And then I’ll tell you to ignore all that and go with your gut.

Factors in choosing what book to write

You could score each possible book idea one each of these clear criteria, but each has its downsides.

• Size of audience. It makes sense to aim at a large segment of potential buyers. But there’s a problem: your book for “digital marketers” or “people with imposter syndrome” is going to have to compete with hundreds of other books for that mass audience. Even so, you don’t want to aim too small: books for “birders who are ready to embrace Bitcoin” won’t sell too well.
• Timeliness. Catch the wave of a new phenomenon and your book could take off. But timing is tricky. It’s easy to be too early (ask the people who wrote books on Google+) or too late (books published in 2026 about AI, for example). Traditionally published books can take two years to get into print, which makes a strategy focused on being timely virtually impossible.
• Affinity with your existing audience. If you’ve already written a book or have a popular blog, Substack, or podcast, then you have a built-in audience eager to hear more about your established topic. So you could write just what they’re expecting. The challenge with that is that it’s hard to come up with something new to say. You may also find it boring to keep writing about what you’ve already written so much about.
• Originality. All other things being equal, a book about a new idea is more likely to capture the imagination of readers. Of course, every new idea has risks. Your new, untested idea could easily be wrong.
• Source material. “Write what you know” is the common cliché. But there’s some truth to this concept: the clients you help every day are telling you, with their inquiries, what problems you should be solving next. The problem is, the more you write based on common, current issues, the more likely that your book ends up too boringly practical. If you anticipate and try to solve problems that haven’t yet emerged, you’ll need to conduct extensive research, and you risk getting too far out ahead of your market.
• Revenue potential. Some book ideas seem tailor-made for generating author revenue through speeches, consulting, workshops, or lead-generation. Just keep in mind that books that are too overtly commercial don’t tend to sell; nobody wants to spend time reading a sales brochure.
• Whatever your publisher (or agent) asks for. If you’ve already been published and had a success, your publisher probably wants another book “like the first one.” But what does that mean? Same topic? Some tone? Same disruptive attitude? Your publisher’s or agent’s instincts are no more likely to be exactly on target than anyone else’s.
• Passion. You could just write about what gets you excited. Of course, maybe nobody else cares about whatever’s motivating you right now. And what happens if you get started on that topic, and then lose interest?

The solution to this impossible puzzle

There’s no way to determine which of these factors is most important. And as you’ve likely noticed in my analysis, every choice you make for rational reasons has its risks and downside.

So here’s my advice:

Write what makes you excited. Write what motivates you. Write what you think will help the most people, will cause them to sit up and take notice.

Write what you think is cool.

Why?

Because you’re going to have to live with this topic through hundreds of hours of work, through waves of self-doubt, and through shifts and pivots as you learn more about the topic.

If you love the topic, you’ll be able to withstand that and lean into dealing with it. If you don’t, you’ll run out of steam and the book will never cross the finish line (or worse yet, you’ll be totally sick of it when it does).

But here’s one more piece of advice.

Pay close attention to whether you keep feeling excited about your writing.

The idea that infatuated you may lose its luster after a few months of research. Better to find that out at the beginning than when you’ve taken the now-hated idea to its conclusion.

So yes, follow your passion. But stay aware of how robust that passion remains.

All the other factors matter. But passion matters more than the rest.