This book deals with the continuous development of the main catalogue of printed books in the British Museum Library, from the decision in 1834 to produce a new catalogue down to the present day.The author examines the peculiarities of the cataloguing system devised by Antonio Panizzi in the 1830's and gradually modified over 150 years, along with its relation to other cataloguing systmes. He describes the production of three complete editions of the catalogue and two editions started but not completed and the controversies which surround them. The treatment of the subject is unique since the author was for over forty years a participant in the events described.