This is a Crystallographic Book List - but what is Crystallography? We take the following working definition. Crystallography is the branch of science concerned with the description and understanding of the structure and properties of condensed states of matter in terms of the spatial relationships of atoms and interatomic forces in an extended array_ Moreover A Crystallographer is a scientist with an active interest in Crystallography, either for its own sake or for the contribution it can make to some other branch of science. (Obviously this defi­ nition is not an exclusive one) The problem of deciding what books should be included in this List made it necessary to think what topics are comprised in Crystallography, and to clarify the issue a draft syllabus was constructed, and is set out below. Though it probably covers too wide a spectrum for anyone indivi­ dual (or University Department) to deal with in detail, there is no part of it which would not be regarded by some Crystallographers as quite essential. It is apparent that some topics are central to Crystallo­ graphy - notably crystal geometry and symmetry, diffraction by perfectly and imperfectly periodic structures, methods of structure analysis, and the relation of physical and chemical properties to structure - and others are peripheral, linking the central topics to other fields of knowledge.