THE NORTHERN WORLD: The History and Heritage of Northern Europe, AD 400-1100, edited by David M. Wilson (Abrams, $40). Like the Vikings themselves, this book ranges far and wide across Northern Europe. Each major section is written by a recognized authority -- Wilson, director of the British Museum, discusses the Vikings proper, James Graham-Campbell the Celts, Joachim Herrmann the Northern Slavs. There are also chapters on Norse mythology, Germanic tribes, Anglo-Saxon settlements in Britain, and the Scandinavian heritage in art and literature. With its illustrations, maps and diagrams, this makes a splendid introduction to a time, place and people. THE VIKINGS AND THEIR ORIGINS, by David M. Wilson (A&W Visual Library, $7.95 paperback). For those looking for a budget introduction to the art and lore of the medieval North, this slender volume offers abundant illustrations, many in color, and a brief essay by Wilson, the dean of Viking scholars. VIKINGS! by Magnus Magnusson (Dutton, $18.95). This book grew out of a PBS series of the same name written and narrated by the author. Magnusson, known as a translator of the Icelandic sagas and as a BBC broadcaster, laces together diverse materials about the Vikings in a pleasant, anecdotal way. He also emphasizes the travels and battles of these sea warriors, bringing to bear the knowledge acquired by people who have built and sailed replicas of various Viking sea craft.