This advice is right on target, so how good must the rest of the book be?
Here are a few things to do to a simple black frock to give it the spice of variety:
1) If it is a dress with a collar, have two or three collars in different colors and alternate them. Be sure at least one is white; for there is still nothing in the world more "appetizing" than a black dress with a fresh white collar.
2) If it is a collarless dress, vary it with colorful scarfs. This doesn't mean rushing to a shop and buying a handful. Be a critical collector of scarfs. When Aunt Mary asks you what you want for your birthday, ask for a scarf. If you see an extraordinary bargain, treat yourself to it. If you make your own clothes, or have them made, remember that the leftover fabric of that pretty sheer or that attractive print will make a good little triangle to knot softly at the neck of your black frock. And remember that many women who think they can't wear black would find it enormously becoming if they would just wear a dash of color with it.
3) If it is a frock with a very simple blouse, you can often wear a plastron or "topper" over it. These should be chosen with greatest care. If you are slender, white is always effective. But if you are inclined to be somewhat chesty, choose a soft, dull color. If you are really large around the bust, do not use this particular way to camouflage your black frock.
4) Jewelry is another means to variety. A necklace of several strands of pearls will make a black dress look more formal and dressy. A necklace of gold or silver (with or without colored stones) is less formal but equally attractive. Strings of colored beads (they can be very inexpensive; just be sure their color is becoming) will work wonders. Or use a pair of nice clips, instead of any of the necklaces.
5) One of the best tricks is to add a gay little jacket to a black frock. If your print ensemble has a black background with bright flowers or a colored background with plenty of black in the pattern, by all means try the jacket over your black dress. If you cannot decided whether you like it, try hanging them together on a coat hanger and placing them where you can step away and examine them. If you saw them together in a shop, would you buy them? If so, by all means wear them together. If not, scout around for another jacket. It may be the bolero of your evening frock, or an extra jacket which you can buy or make yourself.