The National Trust’s many historic buildings range from country houses to vernacular architecture, industrial archaeology and literary shrines. More than 150 of these properties contain books, for the most part the historic collections of their original owners. Though, in common with other heritage bodies, the Trust has been rather slow to realise the importance of its books, these libraries together represent something equivalent to the rare books collection of a national library. They are an incomparable though extremely fragile resource for the history of private book ownership, besides containing many rare books, and others of great beauty and interest.