IPAC (the International Personnel Assessment Council) is making available, free of charge, a monograph by Dr. Charles Sproule titled Rationale and research evidence supporting the use of content validation in personnel assessment.
Having seen a copy, I can tell you it's chalk full of great content, spanning much of the field of personnel assessment, including updated information on validity coefficients and special sections for several different types of tests (e.g., interviews, training and experience exams).
It's a great primer for anyone who wants to learn more about what it means to "validate" an exam, and it's a worthy addition to the library of any seasoned professional.
The monograph can be accessed here if you are a member, or you can request a copy here if you are not. Check it out!