"Four-color printing?!" you say. "I don't want four-color printing! My book has more than four colors in it!"
No, actually it doesn't.
CMYK stands for cyan (blue), magenta (red), yellow, and black. Those of you who remember your preschool color-mixing will recall that you can create all the other colors (or, technically, a hell of a lot of them) with blue, red, yellow, and black.
These are the four colors meant when we talk about four-color printing. CMYK printing is the norm.
That's not to say that I haven't worked on books that were not printed in CMYK.
Sometimes a book will call for a special color-- for instance metallic ink on the jacket-- or, as in the case of Chris Barton's book on the brothers who created day-glo colors, the book requires specific colors that you cannot achieve with CMYK.
Nickelodeon's orange? That's a special color. Gap's blue? Special color. Starbucks' green, Barbie's pink... these special colors are usually achieved with Pantone colors. They cost a bit extra.
Here's a color game: Kitten's First Full Moon was expensive to print. Have you wondered how they achieved such a rich black and white look? How many unique colors do you think went into the printing?Answer: seven!