Truly mastering the nuances and practice of book design takes at least one well-stocked library and one long lifetime, but everybody has to start somewhere. With this last installment of my three-part introduction to book design, I close what I hope will be a useful starting point for the aspiring book designer and curious browser alike.

Last week we focused on designing the body text -- the text that makes up the bulk of the book's content. This third installment primarily looks at display type and front and back matter.

Display Type
At a glance, it's easy to say what "display type" is: anything that's not running text. But there are lots of different ways to use display type in a book, from the subtle to the splashy. As with any aspect of book design, the display type should not be just a place for the designer to show off; it should serve a purpose for the reader.

The most straightforward kind of display type is heads, which are attached to the text and serve to guide the reader. With technical books in particular, some designers revel in a downpour of head styles and sizes and variations, which are intended to reflect the complex organization of the information the book presents. But how many levels of head and subhead does any reader truly notice and distinguish? From my own experience, I'd say the maximum is three and that limiting the heads to two levels, one big and one small, is better still.

When I'm talking about heads, I mean heads within the text -- not chapter titles or subtitles, which are conceptually separate. (I know that some publishers like to number their heads starting with the chapter title as level one, but this has never made any intuitive sense to me, and I discourage it.)

To distinguish different levels of heads, it's best to use two kinds of contrast at the same time: not just a change of type size, for instance, but a change of type size and a different position on the page, or a change of size and a change of weight or style.

Don't rely too heavily on differences in type style, such as changing from roman to italic, or from a serif to a sans-serif typeface: It's amazing how few readers will notice such changes. A favorite device is to use Helvetica for a run-in sidehead (that is, a subhead that's run into the text, rather than sitting above it or beside it) in a paragraph of Times Roman text. Despite the obvious differences in the letter structure of the two typefaces when you look at them closely, they don't stand out from each other enough in a page of text; the change just creates an impression of clutter and disorder. If you add a change of weight to the change of style, however, then you've created enough contrast to make the difference obvious: Helvetica Bold (better yet, Extrabold) subheads in regular-weight Times Roman text stand out quite clearly.

Text Is More Important than Display
Assuming you've designed the text block -- the rectangle formed by the lines of text on the page -- for easy reading, the display type shouldn't intrude on this text. Once you've got a comfortable line length for the text, leave it alone. There's a very common practice, especially in magazines, of letting a picture or a bit of display type (such as a pull-quote) push into the text block from one side or another, forcing the text to wrap around the intruding shape. This can be done effectively, but most often it just means that for the depth of the intrusion, the text has to fit itself into a column that's too narrow, with the kinds of awkward spacing you might expect. It's far better to design a multicolumn layout, and to let the artwork or other display items occupy the width of a whole column (or several columns), rather than to vary the width of the text to accommodate the pretty pictures.

Be Consistent
Whether your display type is a series of carefully modulated heads or a wild array of call-outs, banners, and thought balloons, you'll help your reader by treating the same kind of elements the same throughout the book. Consistent treatment of related elements is essential to making the structure of the book clear to the reader.

Simplify the structure as much as possible, and use contrast to make it very clear what's what. That, along with good text typography, sums up the most important principles of designing a complex book.

No Bells, No Whistles
All too often, someone designing a book that's not complex -- one that consists of nothing more than chapters of prose -- tries to jazz it up by giving too much attention to elements that aren't important. The chapter opening is a good place to be a little flamboyant, but it's only there for the convenience of the reader; a flashy chapter-opening page that isn't easy to read, or that interrupts the reader and grabs the reader's attention, is a mistake.

Among the most annoying examples of misplaced creativity are the overly elaborate page number and running head or running foot. (For simplicity's sake, I'll call them all "running heads" from now on, no matter where on the page they may fall.) The only purpose of the page number is to help the reader navigate; the same is generally true of a running head, though these days there may be another use for the latter: to provide an indication of the source of photocopied pages. Fancy treatments of either page number or running head are self-defeating. They just get in the way. The information should be small and unobtrusive; it simply has to be there when the reader needs it.