In traditional book design, facing pages should be balanced. That is, they should be the same depth. This rule does not apply at the end of a chapter, but it applies almost everywhere else. So when you are laying out a book (or evaluating a layout job someone did for you), you should always view it as a series of two-page spreads, with the odd-numbered page on the right (“recto”) and the even-numbered page on the left (“verso”), and you should check that the text block starts at the same place at the top of every page (with the exception of chapter pages) and that facing pages end at the same distance from the bottom of the page.

Nominally, you want all pages the same depth throughout the book. That is, you want to maintain a consistent bottom margin. However, there are considerations that can make this trick hard to pull off. So the commercial standard is this: Facing pages must balance; however they can run one long or they can run one or two lines short of the nominal margin. However, two successive spreads cannot vary in depth by more than one line.

What does this mean? Well, suppose pages 8 and 9 are one line short. Then pages 10 and 11 can be two lines short or they can be one line short or they can be the normal depth, but they cannot be one line long.

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[Brian Jud invited me to contribute short articles on book interior design to his Book Book Marketing Matters newsletter, a biweekly e-zine. This page is adapted from one of those articles.]