This book is ideal for you if you have access to a computer with Bash installed or available, and you've maybe even used Bash or another Unix-like command shell before to enter at least a few basic commands, but you can't understand the official Bash manual page very well (or at all). You should not be ashamed of that; it's one of the most famously dense manual pages for software ever written! Some experience with basic programming structures such as variables, expressions, conditionals, and loops will help you understand the book—but Bash mostly has its own way of doing things that you need to learn from the ground up, so you don't need to be an expert in any given language.
Alternatively, you may be a more experienced systems administrator, or even an expert in another programming language, who has done a fair bit more than a beginner with shell script, but is still frustrated by the dark corners and difficulties in using it, and wants a course in "remedial shell script" to unlearn some bad habits. The book will clarify arcane and difficult syntax and patterns in shell programming. You'll become much more confident in using it in your work when the situation calls for it, and you'll be in a position to fix both your own and others' shell scripts, and even to train others on writing shell script effectively.