This is a very readable math textbook. Professors will find lots of excellent material for side projects here. Most is particularly appropriate for linear algebra students, but there are also bits and pieces of statistics and combinatorics.
Mathematicians with a research (or hobby) interest in generating rankings will particularly enjoy having all the available details of many well-known ranking systems collected in one volume. The math is all here, along with the motivation, the practical issues to be considered in applications, and a wealth of well-chosen examples.
The level is appropriate for, say, an undergraduate math major in the junior year. I think such a student could learn a lot even by skimming this book: One gets a very clear idea of the reality of applied math -- how the objective, concrete results of the various ranking methods depend on the subjective hypotheses and value judgments made along the way.
Highly recommended.