For anyone WI10 has been concerned with X-ray analysis since its early days, it. is fascinating to see how the subject continues to grow and ramify. The present book is a striking illustration of this development. Although it deals with only one branch of crystal analysis, the study of polycrysta]line materials, it has been found desirable tQ invite some thirty experts to make their contributions in order that each aspect of the subject might be covered in an authoritative way. That it has been possible to weld contributions from so many authors into a coherent scheme is both a tribute to the editors and an excellent exalllple of that happy collaboration that has existed froITi the very beginning amongst X-ray crystallographers and continues so manifstly at the present time.