While Borrelia species cause classical relapsing fevers, this book is mainly about the Lyme disease pathogen Borrelia burgdorferi. This emphasis reflects the remarkable flowering of knowledge and understanding, especially at a molecular and cellular level, that has accumulated over the past three decades since the isolation of this fascinating spirochaete. The spirochaetes are extraordinary bacteria, typified by Treponema pallidum as the uncultivable and mysterious agent of syphilis. Mystery also featured in clusters of childhood arthritis around the small town of Lyme, Connecticut, in the 1970s, which hard science showed were caused by the tick-borne spirochaete. The book gives an encyclopaedic account of this riveting story of modern biology, contributed by experts, many of whose career in science has spanned the whole era from discovery through to deep understanding of the pathogen. It is a fabulous resource for those in the field and full of surprises and insights for the outsider.