Begin with the reader’s moment of use.
Ask what the finished book needs to do. Long-form reading, a children’s picture-book experience, a photography sequence, a reference manual and a gift edition each put different pressure on the format. Consider where the book will be held, whether it needs to travel, how long a reader will spend with it and whether it will live on a shelf, a table or a display stand.
Choose portrait, landscape or square by how the content behaves.
Portrait formats can support a familiar reading rhythm; wider formats can give diagrams, spreads and horizontal images more room; square formats can create a balanced frame for selected image-led work. None is automatically more professional. Look at the natural shape of the images, tables, panels and text blocks you have, then test whether the reader can follow them without cramped captions or awkward empty space.
Build the interior at the intended finished scale.
A layout that looks comfortable on a large monitor can feel very different in print. Review type size, line length, margins, captions, page numbers, illustration labels and important content near the edge at the proposed finished size. If a spread, full-bleed image, activity page or comic panel carries key information, include it in the first review rather than treating it as a late exception.
Let the interior settle, then finalise the cover.
The final page count, section order and confirmed construction affect the cover dimensions and any spine artwork. Early cover concepts are useful for direction, but a final wraparound cover should wait until the interior is sufficiently stable. This avoids a cover being built around a page count or spine allowance that no longer matches the work. Once the working format is settled, use the Book Cover & Spine Setup Guide to plan the final wraparound artwork.
Test a decision with a real-size review.
Print a simple working dummy at the proposed scale where that is practical, or review a proof with the finished size clearly in mind. Hold it as a reader would. Check how dense pages feel, whether photographs have enough room, where the eye lands at a page turn and whether the book feels right for its purpose. A test is more useful than choosing a trim only because another title used it.