Artists/the arts; British Cathedrals, by Paul Johnson. New York: William Morrow & Co. $24.95.

A comprehensive study of the architecture of 90 of Britain's cathedrals, this book is both scholarly and entertaining. Johnson demonstrates that cathedrals were "built from the inside out": determined be religious requirements and the dictates of technology and fashion. Detailed and inspired descriptions of these awesome structures are balanced with lively discussions of the communities that built and supported them. The book concludes with a comment on modern cathedrals and the controversial topic of restorition. Until the reader becomes comfortable with the technical terminology (defined in the glossary), the book tends to be slow-paced. Though not always well-placed within the text, the 194 plates, 24 in color, are well chosen to reveal both the skill and inspiration of the builders.