Books-Across-the-Sea started just after World War II when The Outpost, a group of Americans stationed in war-torn England, saw a need to replace American books destroyed in the war. At their request, a group of book-minded Americans rushed 70 books to the U.K. The books were welcomed as Ambassadors and London responded by sending 70 books in exchange. The books chosen reflected the life and culture of each country. The English-Speaking Union took over the program in 1947 under the chairmanship of T.S. Eliot.

The exchange has grown over the years to include shipment of the Books-Across-the-Sea volumes to many of the international ESU's. Categories for selection of the books are: Fiction, Biography & Autobiography, Poetry and American Studies. A panel selects one book in each category as an Ambassador Book. Authors of Ambassador Books are honored at a reception and receive prizes.

Past recipients include Arnold Rampersand, Tom Wolfe, Grace Paley, Doris Kearns Goodwin, John Updike, Michael Beschloss and David McCulloch. When the program celebrated its 25th Anniversary the panels on each side of the Atlantic chose the best biography written in each of the 25 years. Copies of these volumes form The Nerney Collection which is housed in both the U.S. and British ESU headquarters.