[.ca] Principles of Protein X-Ray Crystallography (ISBN 0387333347)

Decent text, but better Crystallography books are out there.:
Drenth is a decent enough book. The figures are ok, nothing great. They mostly just drive home the point made in the text, but are not instructive in and upon themselves. If you are looking to get a basic understanding of X-Ray crystallography and its uses to solve protein structure try the Gale Rhodes book. If you are looking for a more rigorous book try the Michael M. Woolfson book. Drenth tries to be the middle ground between the two. The subject though is too complicated to do it justice like that. Either keep it simple or go in depth.

Best introductory text:
Best introductory text for macromolecular xray crystallography. Simple and succinct mathematical explanation of basic concepts. It provides enough background for students to start a research project.