The Index Translationum is a "World Bibliography of Translation." It contains cumulative bibliographical information on books translated and published in about one hundred of the UNESCO Member States since 1979 and totals more than 2.000.000 entries in all disciplines: literature, social and human sciences, natural and exact sciences, art, history and so forth. The database is updated regularly.
Since most U.S. libraries don't collect foreign translations of English-language works, the best way to find out if an English-language author's work has been translated into a foreign language is to go to the national library of the country where the foreign language is spoken via Libweb. This is the most comprehensive international listing of library web servers that I know of.
For example, if you wanted to find a listing of John Steinbeck's works into Swedish, you might...