I pair this text with one on IRT in my graduate psychometrics course. This classic text provides an excellent overview of classical test theory in concise, no-nonsense terms while still being easy to read for an audience of non-statisticians. The chapters are well-organized with helpful study aids.
The book begins with a brief introduction to psychological/educational measurement and a bit of history. The second chapter is a review of basic mathematical concepts. The fun really starts in chapter 3 with the basic propositions of classical test theory and a list of results--this chapter is a marvel of brevity and clarity. The next chapters on reliability (ch. 4), validity (ch. 5), test construction (ch. 6), and equating (ch. 7) build sound practice upon this sound theoretical foundation. Scaling issues are covered superficially in chapter 8 and then a number of important issues are raised in chapter 9 ("Special Considerations..."). The final two chapters ("Controversies and current developments..." and a chapter on IRT) are most dated and least helpful (although, like the rest of the text, the material is covered well and these chapters would serve as a good foundation for understanding recent developments).
In comparison, other psychometric texts tend to be more comprehensive at the expense of being quite shallow. These other texts, which also tend to be verbose, may be better-suited to undergraduate courses designed to gently introduce unsophisticated students to the bare basics of measurement. Allen & Yen is better suited for serious undergrads and graduate-level students who wish to understand classical test theory and to apply it well.
Special note for specialists: while this book includes many issues critical to designing selection tests, industrial psychologists and HR professionals will need additional training on selection (e.g., job analysis) and on legal issues; other specialists will probably also find the book to be quite focused on measurement.
Special note on versions: I own both the 1979 burgundy hardcover and 2001 blue-black paperback editions and, as far as I can tell, they are identical.