It's not just about hyphenation. Typesetting a book includes eliminating "widows" and "orphans" (lines isolated from their paragraphs by page breaks, and final

It's not just about hyphenation. Typesetting a book includes eliminating "widows" and "orphans" (lines isolated from their paragraphs by page breaks, and final lines of paragraphs with only one or two words) as well as "rivers" of whitespace that can occur when spaces between words inadvertently line up vertically, and the stretching / compression when a line has more or fewer words than average. This is done by adjusting where line breaks fall. Basically, in a well-typeset book, nearly every line break is a manually selected hard break rather than an automatically generated soft wrap.