Motor City: troubles and success story; Mustang -- the Complete History of America's Pioneer Ponycar, by Gary L. Witzenburg. Produced by the staff of Automobile Quarterly. Princeton, N.J.: Princeton Publishing, Inc. $27.95.

When Ford Motor Company put the Mustang on the road in 1964, it launched a new era: the "ponycar." Before the year was out, the company sold well over 400, 000. The car was so successful, in fact, that it helped propel Lee A. Iacocca, then head of Ford division, into the presidency of the company in the 1970s.

The Mustang was the most exciting new Ford car since 1949. It changed the company's image.

Some things in life are memorable. You are apt to remember exactly what you were doing at the time of a stunning event -- even in the automobile world. To a lot of people, such is the case with the Mustang.

I remember my first ride in one. Perhaps you do, too. It was the start of a new era in Detroit -- a city, and an industry, which have taken a lot os lumps over the years, many because of the city's own shortcomings and its refusal to meet the challenge of the times on the line.

Gary Witzenburg, a Duke University- trained engineer who once worked for General Motors, writes clearly and logically, even if 204 pages is a lot of room for a single nameplate. Nonetheless, if you're a Mustang buff, the book may even be too short.

The author takes you inside the design and engineering rooms and lets you feel some of the excitement and frustrations and sweet dreams of success that filled them.

What made the Mustang an important car was its style and price. In other words, most people at the time could afford to buy one.

"Whatever the outcome, Mustang will remain one of the most important and best-loved cars of all time," Witzenburg writes in the foreword to the book. "Everyone has a fantasy, but too many are out of reach. For millions of people like you and me, Mustang has been so significant partly because it is not."

While expensive, the book is heavy with glossy paper between the covers. Automobile Quarterly produces high-quality publications which are designed to last. These days it has to get its price.

The 22 pages of color pictures are worth a lot of the cost.

Included at the back of the book are production and sales figures, engines year by year, optional equipment, road-test performance results, colors, the car's racing record, and specifications. There is also a general index and index of illustrations.

Witzenburg, a seasoned race driver who has competed in Formula cars, sports cars, and sedans, left engineering for journalism in 1973. "Mustang" is his first full- length book.