Every school kid in America knows about the Lewis and Clark expedition, but hardly anyone in Britain has heard of it. This is a shame; it was not only an important journey of exploration, but a wonderful adventure story as well.

In 1803, in the deal of the century, Thomas Jefferson bought the French- owned Louisiana Territory from Napoleon for a paltry $15m and more than doubled the size of his country for just 3 cents an acre. However, no European or white American knew what lay within that vast strip of hinterland west of the Missouri river. So Jefferson commissioned a military expedition to find out. He asked Lewis, the leader, to make a comprehensive study of everything they came across: flora, fauna, minerals and the Indian peoples, always reassuring them that the expedition was "innocent".

Above all, they were to find a north-west passage connecting the Missouri and Columbia for the purposes of commerce. No such passage existed, of course; the Rockies separated the rivers, and nearly cost the Corps their lives. None the less, in 1804-5 Lewis and Clark succeeded in leading three dozen people, including an Indian woman and her baby, to the Pacific and back. They wrote volumes of journals and notes, making it the best- documented expedition of the quill and inkwell era.

This book is a by-product of an American TV documentary made by Ken Burns, famous for his Civil War series, and Dayton Duncan, the scriptwriter. It includes many illustrations and contributions by other writers, plus quotes from the soldiers' own vivid journals. Unfortunately, the main text, diaries and captions often repeat themselves. All contributors are uncritically admiring of the men and their exploits. They were indeed admirable, but hero-worship does not allow for an explanation of Lewis's suicide three years after their homecoming, nor for Clark's surprisingly cruel treatment of his slave, York.

The very success of the expedition raised problems that get no discussion here. For example, the lethal policy of the US towards native peoples was inscribed in this "innocent" foray, and the personal decency of Lewis and Clark could not save their achievement from having a destructive legacy.

However, we should be grateful for this book. Little pictorial material exists from Lewis and Clark's day, so the authors have used paintings and photographs from later decades, such as the work of Kari Bodmer, who studied the Plains Indians of the 1830s. Like Lewis and Clark, these recorders of the Western frontier and its people deserve a British audience.