Concrete Mathematics is essentially the mathematics needed to study analysis of algorithms. From the preface:
One of the present authors had embarked on a series of books called
The Art of Computer Programming, and in writing the first volume he
(DEK) had found that there were mathematical tools missing from his
repertoire; the mathematics he needed for a thorough, well-grounded
understanding of computer programs was quite different from what he'd
learned as a mathematics major in college. So he introduced a new
course, teaching what he wished somebody had taught him.
So yes, there are practical applications. And recurrences are a recurring theme, but there's more to it than just that.
It's not just about recurrences. Although, It looks like this at the first glance. This book will give you mathematical mindset which you will be able to apply in practice (while working with algorithms).
Each chapter in the book is written in essay style, authors gave you very curious math pearls, and teach you how to think by using these examples.
I have the impression that it is mostly a book that teaches you techniques of how to solve recurrences. Am I wrong?