“I think I figured out who the doubters are.” That’s what a reader emailed me after I released my newest book, Four Doubt.

She followed up that sentence by saying, “But I found more than four doubters in this book. If I counted correctly, there were at least eight. It was like everyone had doubts. Did you realize that?”

I write series, so as a way of making it easy for my readers to know which book to read next, and also as a way of having an author “brand,” I include the number of the bo...