The wry observation attributed to George Bernard Shaw that "England and America are two countries divided by a common language" finds support in The Cambridge Guide to English Usage. Author Peters, of Macquarie University in Australia, provides evidence that their common language also divides Canada and Australia from the other countries.

Within the A-Z arrangement of brief, to-the-point articles, entries on catalogue and catalog, dived and dove, fitted and fit, freshman and fresher, titbit and tidbit celebrate transatlantic differences, some rather subtle, others more pointed. Peters draws on a range of authorities for her judgments on usage. Those include large databases, such as the 140-million-word Cambridge International Corpus of American English, and other usage guides from throughout the English-speaking world. In line with the most recent of these other handbooks, as well as the irrefutable evidence of present usage, Peters takes a descriptive rather than prescriptive approach. Her analytical discussions of parts of speech, grammatical concepts and constructs, and the like explain the origins of rules but also provide contemporary and historical examples of how usage tempers some rules.