Interior Book Design: What Makes a Professional Book Interior

Interior book design is everything a reader sees between the covers: the size of the page, the margins, the typeface, the space between lines, how each chapter opens and where the page numbers sit. Readers rarely notice a well-designed interior. They notice a poor one straight away, even if they can't say why. This guide walks through what a professional book interior is made of, the tell-tale signs of a homemade one, and how to decide whether to design it yourself or hire someone.

Key takeaways#

• Interior book design covers trim size, margins, typeface, leading, chapter openers, running heads, page numbers and front and back matter.
• Good interior design is invisible: it lets the reader forget the page and follow the words.
• Platform rules set the minimums, such as KDP's 7-point minimum font size and margins that grow with page count, but a professional interior goes well beyond them.
• The commonest amateur signs are tight margins, document-style fonts, double spacing, inconsistent chapter openers and stray lines at the tops and bottoms of pages.
• A simple novel can be designed well in Word. Books with images, tables or complex structure are easier in professional layout software.

What is interior book design?#

Interior book design is the set of visual decisions that shape every page of a printed book. It decides how big the page is, how much white space surrounds the text, which typeface carries the story, how chapters begin, and how readers find their way around. It also covers the special pages at the front and back of the book.

It sits between editing and printing. The words should be final before design starts, because cutting or adding a few paragraphs later can shift every page that follows. And it is separate from the cover, although the two should feel like they belong to the same book.

You will also hear the words formatting and typesetting. Typesetting is the page-by-page craft of setting the text: line breaks, hyphenation, spacing and fixing awkward lines. Formatting is the practical job of turning the design into files that KDP and IngramSpark accept. Our guide to what typesetting is explains the difference in more detail. Interior design is the plan that both of them follow.

The parts of a professional book interior#

Trim size

Everything starts with trim size, the finished width and height of the book. It controls line length, page count, spine width and print cost. KDP lists 6 x 9 inches as the most common trim size in the US, and it offers smaller sizes such as 5 x 8 and 5.06 x 7.81 inches that suit many novels. Choose the trim size before anything else, because changing it later means redesigning every page. If you haven't decided yet, read how to choose a book trim size.

Margins and the gutter

Margins frame the text and protect it from the trimming blade. The inside margin, called the gutter, has a second job: keeping words out of the spine fold. On KDP the minimum inside margin grows with page count, from 0.375 inches for books of 24 to 150 pages up to 0.875 inches for books of 701 to 828 pages. The top, bottom and outside margins must be at least 0.25 inches without bleed, or 0.375 inches with bleed. IngramSpark recommends at least 0.5 inches on all sides of the text block.

Those are minimums. A professional interior usually gives the text more room than the platform requires, because generous margins make a page feel calm and expensive, and they give readers somewhere to put their thumbs. Our guide to KDP margins and gutter has the full table.

Typeface and size

Body text should be set in a typeface designed for long reading, usually a serif such as Garamond, Minion or Caslon for fiction. Fonts made for screens or office documents can look heavy and cramped in print. Decorative fonts belong in chapter titles, if anywhere, not in the body.

KDP requires a minimum font size of 7 points, but that is a floor, not a guide. Most novels are set somewhere around 10 to 12 points, depending on the typeface, since some fonts look much larger than others at the same size. Whatever you choose, the font must embed in your PDF. Both KDP and IngramSpark say every font must show as embedded, and some free fonts won't embed because of their licence.

Leading and line length

Leading is the space between lines. Too little and the lines crowd each other. Too much, like the double spacing many manuscripts are written in, and the page looks like a school essay. Book interiors usually sit a little above single spacing. Line length matters too: lines that run too long make the eye lose its place, which is one reason a 6 x 9 book with narrow margins can feel tiring to read.

Chapter openers

The first page of each chapter is the most designed page in a novel. Most professional books start chapters partway down the page, called a sink, with a styled chapter number or title, and often a drop cap or the first few words in small capitals. The details are a matter of taste. What matters is that every chapter opens the same way.

Running heads and page numbers

Running heads are the lines at the top of the page that carry the author's name, the book title or the chapter title. Page numbers, called folios, sit at the top or bottom. Convention removes both from chapter openers and blank pages, and the page count usually starts in the front matter, even where no number is printed. Getting this right in Word takes careful use of section breaks, and it is one of the first places amateur interiors give themselves away.

Paragraphs and scene breaks

Printed fiction indents each paragraph except the first one in a chapter or after a scene break, and it doesn't add space between paragraphs. Scene breaks are marked with extra space or a small ornament, so the reader can see that time or place has changed. Blocky paragraphs with gaps between them are a web convention, and they look out of place in a novel.

Front and back matter

The half-title, title page, copyright page, dedication and contents all need their own layouts, and they come in a set order. So do the acknowledgements, author bio and any back-of-book offers. Our front matter checklist shows what goes where.

Signs of an amateur book interior#

If you are checking your own proof, or comparing your book with ones on your shelf, look for these:

• Text that runs too close to the edges or disappears into the spine.
• A default document font, often at 12 points with double or 1.5 line spacing.
• Spaces between paragraphs as well as indents, or no indents at all.
• Chapters that start at the very top of the page, or start in a different way each time.
• Page numbers and running heads printed on chapter openers and blank pages.
• Single lines of a paragraph stranded at the top or bottom of a page.
• Pale gaps running down justified text, called rivers, where word spacing has stretched.
• Blurry images. KDP asks for images of at least 300 DPI.

None of these will get a book rejected on their own. Together, they are what makes a reader decide a book is self-published before they have read a page.

Designing your book interior yourself#

You can produce a clean interior yourself, especially for a text-only novel. Start with these steps:

1. 1Finish the edit. Design last, after the words are locked.
2. 2Set the trim size and margins first, using your platform's minimums as the floor, not the target.
3. 3Build everything from paragraph styles, so body text, chapter titles and scene breaks stay consistent.
4. 4Pick one book typeface for the body and, at most, one more for headings.
5. 5Use section breaks to control running heads and page numbers.
6. 6Export a PDF with fonts embedded, and check it in Adobe Acrobat's document properties.
7. 7Order a printed proof. Problems that hide on a screen are obvious on paper.

Our guide on how to format a book in Word walks through the Word side step by step. If you're publishing on IngramSpark as well as KDP, check its file rules too, because it asks for PDF/X-1a or PDF/X-3 files and a more generous margin. See how to format a book for IngramSpark.

When to hire a professional#

Hiring a designer or formatter makes most sense when the book has images, tables, multiple heading levels, poetry or workbook pages, when you want it to sit beside traditionally published books without looking homemade, or when you would rather write the next book than learn layout software.

At HMD, our book formatting service is human typesetting in Adobe InDesign with page-by-page quality checks, not a template. Packages start at £197 ($249) for Clean & Simple, up to 20,000 words. Enhanced Layout is £297 ($377) for up to 40,000 words, and Complex Design is £397 ($497) for up to 60,000 words for non-fiction and workbooks. Longer books get an exact fixed quote within one business day. Every package includes a print-ready PDF and a reflowable EPUB, three revision rounds, and files prepared for KDP and IngramSpark. We'll format your first chapter free before you buy, so you can judge the design on your own words.

The interior and the cover should look like they came from the same publisher. If you also need a cover, our cover design service can match the cover typography to your interior.