
The first author (Sedgewick) is renowned in the field of Algorithms. The authors illustrate the algorithms and data structures using the Java programming language. As long as the reader has some kind of programming background, this should not be a problem as the authors abstract away the complexities by using only a small subset of Java. For a more slower-paced introduction to the material, it is better to consult their introductory book: An Introduction to Programming in Java.
As already pointed out, even if the reader is not familiar with Java, this book can still be used as most of the code is similar to pseudo-code and the authors use a lot visuals to make sure that the reader understands the algorithms and data structures. He can use a language like Python to re-implement the algorithms to solidify his understanding.
What I really liked about this book is the support site that the authors maintain at:
http://algs4.cs.princeton.edu/home/ It contains brief summary of the chapters, downloadable code and solutions to selected exercises.
I would definitely recommend this book if you are looking for an introductory book on algorithms and data structures.