What is a sidebar?

The purpose of a sidebar in a book is to package up important details that would otherwise interrupt the flow of a chapter.

For example, you might use a sidebar for:

• Collating examples that aren’t essential to the text.
• Explaining a technical concept that some readers will find interesting, but not others.
• Organizing and explaining historical context for a concept, potentially including a timeline.

A sidebar is typically indicated typographically by setting aside text in a box or with a shaded background. Designers may also make it stand apart visually by using a different typeface, for example sans-serif type in a book where the body text is set in a serif font. And every sidebar needs a heading, so the reader knows what the extra text is about (and whether it’s worth reading).

Sidebars can be seductive to authors because they allow you to show off detailed content without disrupting the main narrative. But don’t get carried away. A book with lots of sidebars is confusing to read.

Essential questions if you’re considering including sidebars

Here’s a checklist you should use before including a sidebar in your book:

• Is this content actually useful to the reader? If not, just leave it out. Every bit of text you include needs to be copy edited, proofread, and printed. It’s better to avoid this overhead completely if the only purpose of the sidebar is to show off the depth of your knowledge.
• Does this content belong in the chapter? If the reader would benefit from this extra content, but not necessarily at the point in the chapter where you currently have it, there are other ways to include it. You could post it online and include a link, or stick it in the back of the book as an appendix.
• Could this be a footnote? Sidebars are typically at least half a page; if smaller, they will look odd and distracting. If the extra content is no more than a few sentences, consider making it a footnote instead.
• Does this belong in the text? A sidebar signals “This content is optional, you can skip it if you want.” If you can actually include the content in the text without distracting the reader, it’s better not to segregate it as a sidebar. For example, you could include a short section called “Three steps to implement xxx” and list the three steps. Readers who aren’t interested could easily skip this short section, but others will benefit from it.

If you do include a sidebar, make sure to reference it in the text. For example, “(If you’re interested in the historical context that led to this standard, see the sidebar “A historical timeline of the Xxx standard.)”

Don’t make a fetish of sidebars; use them sparingly. But if you’ve got a chunk of information that’s begging to be in the book, but doesn’t seem to fit the narrative, a sidebar may be the tool you need to signal that to the reader.