The book block: In a book, the text is confined to a tightly-defined area on the page called the book block, where facing pages usually end on the same line. The exception may be the last page of a chapter.

Margins: The white space around the entire book block. White space is important and generous margins around the book block allow the eye to move comfortably from one line to the next

Alignment: Text must line up across the page. Book designers spend a lot of time adjusting the line spacing to make sure this happens, especially if there are headings and subheads, lists and illustrations.

Line spacing: Lines of text that are too close to each other (or too far apart) are difficult to read.

Paragraph spacing: In most cases, there should NOT be a line of space between paragraphs. Indicate the beginning of a new paragraph by indenting the first line. Space above a paragraph can be used sparingly to indicate a scene change or a new section. Whenever there is a blank line above a paragraph, eliminate the first-line indent on that paragraph.

Widows and orphans: The first line of a paragraph shouldn't fall on the last line of a page, and the last line of a paragraph should not go over to the top of the next page. Widowed and orphaned lines make the reader pause, thus impeding reading comprehension.

Lines after a subhead: When a subhead appears at the bottom of a page, it should be followed by at least two lines of text while still maintaining the book block. Like widows and orphans, leaving orphaned headings is a no-no.

Word stacks: Word stacks are when the same word appears in the same position in three or more consecutive lines. These are fixed by adjusting word spacing or rewriting the text.