How to format a book interior
Print a Word document to PDF and upload it. Every word is there, and the book is still wrong. Readers rarely say why. They say it looked cheap, or they put it down two chapters in. What they are reacting to is a set of production decisions a word processor was never asked to make.
Here is what a typeset interior does differently.
A page is measured, not eyeballed
A word processor shows you one page at a time, on a screen, at whatever zoom you left it on. A printed book is a physical object with a fixed line length, and every other decision follows from that line.
Interiors are specified in picas and points — 12 points to a pica, six picas to the inch — because the differences that matter are that small. (Printers have a vocabulary for the rest of it, collected in The words printers use.) Eleven-point type on 13.5 points of leading reads differently from the same type on 15 points, and over 320 pages the gap is the difference between a book that pulls you along and one that feels like work. Neither is visible at 100% zoom on a laptop, which is the whole argument of Proofing on screen or on paper.
The consequence most authors miss: the same manuscript is a different object at each trim size. Go from 6×9 to 5.5×8.5 and the measure gets shorter, so fewer words fit on a line, so the page count climbs and the reading rhythm changes. You set the type to the trim; you never copy numbers from a template built for a different page.
Mirrored margins and a gutter
A word processor gives you a left margin and a right margin, identical on every page. A book has an inside margin and an outside margin, and they trade places as you turn the page. That is what "mirrored" means, and without it every second page is visibly off-center.
The inside margin also has to carry the gutter — the extra space swallowed by the binding, which grows with page count because a thicker book curves harder at the spine. Get this wrong and the last word of each line on a right-hand page disappears into the fold. See Margins and gutters for the working figures.
Justified text, and the hyphenation it needs
Trade books are justified — both edges flush. Justification works by stretching and squeezing the word spaces on each line, and the shorter the line, the more violently it has to stretch.
Justification without hyphenation is the most common flaw in a self-typeset book. With no hyphens allowed, the setter cannot break a long word, so it pushes it to the next line and pulls the remaining words apart to fill the gap. You get gaping white holes, and vertical "rivers" of space running down the page. Turn hyphenation on and those gaps close. Aim for no more than two hyphenated lines in a row, and never a hyphen on the last line of a page.
In the Interior Formatter. Upload a .docx and you get justified, hyphenated, mirrored pages with the gutter set from the real page count — plus a print-ready PDF and an EPUB 3 from the same manuscript. Five interior styles: Literary, Modern, Genre, Compact and Classic. Start your interior → · about the Interior Formatter
Chapters open on a new page — usually a right-hand one
Every chapter starts on a fresh page. That part is obvious. The convention that separates a trade book from a manuscript is that chapters traditionally open on a recto — the right-hand page — which means when a chapter ends on a right-hand page, the next left-hand page is left deliberately blank.
Chapter openers also start low, a third or so down the page. That drop is the visual signal that a new unit has begun, before the reader reads a word. What fills the space it makes — a drop cap, a line of small caps, an ornament, or nothing at all — is the one decorative decision a plain trade book usually allows itself: Drop caps and ornamental chapter openings.
No widows, no orphans
A single line of a paragraph stranded at the top of the next page, or a lone opening line left at the foot of the previous one, is the mark of text that was poured rather than set. The fix is to adjust the lines before it so the break lands cleanly, on every page rather than the ones you happened to notice.
Running heads and folios that disappear
Running heads (author name on one side, title or chapter on the other) and folios (page numbers) run through the body of the book — but they are suppressed in three places: chapter opening pages, blank pages, and the front matter that precedes the main text. A page number printed on an otherwise blank page is one of the clearest amateur tells there is.
An even final page count
Books are printed on sheets folded into signatures. A book ends on a left-hand page, which means the final page count must be even. If your text runs out on page 287, the book needs page 288 — blank, with nothing printed on it. Printers reject odd counts.
Some books are not built like this at all
Everything above describes a trade book: a river of prose, chapter after chapter, the same page repeated three hundred times. A good many books are not that, and for those the page is designed around what the reader does with it rather than around the measure.
Coloring books and Puzzle and activity books are laid out around a pen, which turns paper and show-through into layout decisions rather than printing ones. Printing music and notation and Setting a play or a screenplay each follow a notation their readers know better than you do, and departing from it reads as an error rather than a style. Field guides and reference layout assume a book that is consulted rather than read start to finish. And a manuscript too long to bind in one piece becomes Splitting a book into volumes, which is a set of decisions in itself.
Print and ebook are two files, not one conversion
A print PDF is fixed: you decided the page, the measure, the leading, and it will look the same on every copy forever. An EPUB is the opposite kind of file — reflowable, with the reader choosing the type size, the face and the window width, so there are no fixed pages at all.
This is why a print PDF converted to an ebook always reads badly, and why an ebook exported as a PDF looks like a website. They are two outputs from one manuscript, generated separately with different rules. The page count from the print side feeds the Cover Maker, so your spine matches the book you actually made.
Typeset your book
The Interior Formatter is free to use: name your book, bring your manuscript, and it sets real pages you can read before you commit to anything. You only pay when you want the files without the preview watermark.
Next: Margins and gutters · Also: Front matter order · Choosing a trim size