An excellent supplement to the interest theory portion of the course 2 actuarial examination. Provides many problems and more thorough mathematical explanations of many of the concepts. Some are more detailed than required for understanding of the exam syllabus, but it is still worthwhile to work as many problems as time permits.
I liked the explanations of some concepts better than the standard text for this course (Kellison), but a linear reading of this material would take too much study time away from other topics.
Conclusion: Use as supplemental material, but very useful nonetheless.