With the dollar's recent decline, export opportunities are palpably greater today than at any other time in the past decade. Yet many U.S. companies -- including the vast majority of smaller ones -- still don't know much about opening up those big markets overseas. You'd think there would be a few books designed to fill this information gap.

The good news: there are. The bad news: the gap hasn't disappeared.

It's not hard to find a book on the basics -- matters such as shipping and licensing, locating the addresses of governmental trade offices, finding foreign commercial attaches, learning essential economic data on various countries. Check out Exportise, for example, a highly readable handbook produced by the Small Business Foundation of America. Alternatively, consult Seamus G. Connolly's Finding, Entering and Succeeding in a Foreign Market or Marta Ortiz-Buonafina's Profitable Export Marketing. Both provide useful information, albeit in dry, textbook-like form.

Once you've got the technical information at hand, you'll need a book on what it's really like to do business abroad. How have others done it? What cultural subtleties do you need to understand? Here's where the going gets rocky. Skip The World Class Executive, by Neil Chesanow, and Going International, by Lennie Copeland and Lewis Griggs. Both books try to cover too much ground and are marred by a lack of in-depth case studies. They also have a tendency to overgeneralize about various ethnic groups and their business practices. Instead, look for a book such as Robert C. Christopher's Second to None.

Christopher, a veteran Asia hand who is author of the critically acclaimed The Japanese Mind, concentrates on only one country, Japan. But he knows his stuff, and he's not shy about identifying where companies have gone wrong, as in his description of Apple Computer's disastrous entrance into Japan. Most of his case studies are of giant companies. Even so, anyone considering a move into the capitalist world's second largest market would do well to read Christopher first.

Now all we need is similarly well-informed books about the many other countries that U.S. companies might like to sell to. Until we get them, the information gap will persist

-- Joel Kotkin

The information gap is just beginning to close in business travel guides... One new guide, for example, explains that business cards are so important in Japan that ritual governs their exchange among executives. You, as the visitor, should offer your card first, after an appropriate bow or handshake. Show the card's English side: it indicates respect for your host's facility with our language. Study the cards you get in return and repeat each person's surname; then place them o the table in front of you. Never bend them or bury them in your suit pocket.

It's this kind of practical advice that you get from a new series of business travel books produced by The Economist, the weekly British business publication. The first four volumes, covering Japan, Britain, the United States, and the Arabian Peninsula, impressively fill a void in the genre: other "business" travel books are no more than tourist guides with a new cover.

The Economist Business Traveller's Guides focus in detail on local social and commercial customs, such as appropriate dress, manners, and entertaining, and offer background information on economic and political climates. The longest section of each book is a city-by-city guide describing hotels, bars, and restaurants. It also lists such useful business services as interpreters, secretaries, and international couriers.

The Economist plans four new titles per year; upcoming this spring wil be guides to France, China, West Germany, and Southeast Asia.

-- Stephen D. Solomon

* Exportise, by John C. Rennie (PB, Small Business Foundation of America, 20 Park Plaza, Boston, MA 02116; 1987, $29.50)

* Finding, Entering and Succeeding in a Foreign Market, by Seamus G. Connolly (HC, Prentice-Hall, 1987, $39.95)

* Profitable Export Marketing, by Marta Ortiz-Buonafina (PB, Prentice-Hall, 1984 $9.95; HC, Prentice-Hall, 1984, $21.95)

* Second to None, by Robert C. Christopher (PB, Fawcett, 1987, $8.95; HC, Crown, 1987, $16.95)

* The Economist Business Traveller's Guides: Japan, Britain, United States and Arabian Peninsula (Prentice Hall Press, 1987, $17.95 each)