This book describes the method and steps used to determine crystal structure very well. It also gives a good account of symmetry groups used in crystal structure, better than my lecture notes anyway. However for the actual mathematical treatment of diffraction, this book offers too much discussion and spends a lot of text describing the maths you'll have already known if you've done A-level or Advanced Higher physics. If you're unsure of the basic CSD method and symmetry then get this book, if you do not understand the mathematics of CSD spend your money on another book.