I bought this book when it was originally published back in 1990. I started with little programming experience, and no shell programming experience. It brought me up to speed quickly. I no longer write many shell scripts; however, I still use it as a desk reference when I do. For any UNIX system administrator, this book (or one just like it) is essential.
BTW, I have been looking for a better book all these years and haven't found one. It's not that I think this book is perfect, rather there just aren't many good books on this subject.