In the book and publishing industry, keylines are the fundamental principles that publishers, authors, and other industry professionals consider when making decisions relating to book production, formatting, layout, and design.
Keylines are mainly concerned with ensuring visual coherence and aesthetic appeal. They usually include guidelines on typographic style- type, page layout- how a finished page should look, margins- the space around a block of text, white space-blank areas on a page, and chapter headings or numbering conventions—any aspect of the physical structure of a book or publication.
Typography is one example of this sort of thing. Choosing appropriate typefaces or fonts for your work can be important in establishing genre or tone. Even your intended reader’s age group might dictate whether you opt for serif or sans serif styles. How big you set your type – bodies, headers – how much leading you give it, the space between lines, and whether you use paragraph indents can all affect readability.
Another example would be the page layout itself. The size of the pages will be, and how many words per line? Will there be headers, footers, or folios? Where will they go?
Whether it’s advice about how close to the edge of the paper you should place elements such as text blocks or images – known as margin recommendations – or guidance on line spacing within paragraphs to ensure legibility, keyline advice helps make sure everything comes together visually.