Blow's book is excellent. Another good one is Practical protein crystallography by Duncan McRee 1999 Academic Press. Its ever so slightly out of date on software, but the basics don't change. I think its an easier read for new crystallographers.
Also, check out some great web sites: The Cambridge University Protein Crystallography Course http://www-structmed.cimr.cam.ac.uk/course.html and Berhnard Rupps web site http://www.ruppweb.org/
