This book is not a click-here teach yourself book. IT professionals know that learning a new area of technology takes effort on their part and requires that they apply prior knowledge to gain new knowledge. At the pro level, we don't spoon-feed you! So yes, you will have to dig into the book's code samples and experiment with them. Having said that, however, this book does a great job of explaining its code samples line by line. As noted by other reviewers, the depth of this book exceeds most other books on JSP. IT professionals know and love WROX as one of the very best publishers of books for professionals.
I have used this book to teach JSP at university level multiple times. The student who is willing to roll up his/her sleeves and dig in soon realizes that this is one of the few books that will be kept once the degree is earned. This book allows me to cover past and present JSP methodologies. Learning past methodologies is critical, as you will find millions of lines of past approach code still in use in the real world, and may even need to convert some of it. My students get hired when they finish this course because of this.
Every time I teach JSP, I look for a new textbook or professional book to replace this book. So far, I have not found anything that comes close to the breadth and depth of this book. I'll be using this book again soon.
JSP is not a simple technology, but it is a powerful one consisting of many approaches and supporting many add-on technologies. You MUST be solid in your knowledge of Java and object-oriented programming. If you are not, you are not ready for JSP, period, no matter which book you use.