The book can be used by beginners and experienced people in JasperReports. This book teaches you how to develop reports using iReports, the GUI report designer. The book is full of snapshots which makes learning very easy. There were some errors in some of the snapshots, like on page 200 the values of static text components is not consistent which might be confusing. But overall the snapshots are pretty good.
The first three chapters are very basic, and they are only useful for beginners. If you are familiar with JasperReports, you'll already know things covered in these chapters. From the fourth chapter the book moves to advanced recipes. Beginners might face some difficulties understanding some of these recipes. There is a lot to learn for people familiar with JasperReports in these chapters.
The last chapter covers generating reports from Java code. This chapter covers topics from compiling a report from java code to exporting it to Excel, Pdf or printing it. It also covers how to generate reports from a web application. This topic has some technical errors (not related to JasperReports) like the response content type is not set through a page directive, there should be no HTML tags in the generated content as its a PDF response and the report is generated through a JSP page using scriptlets instead of a Servlet. The JasperReport code is correct though so this is not a big issue. An additional chapter can be downloaded from the publishers site which is a little weird.
Disclosure: I received a copy of this book from the publisher in exchange for writing this review on behalf of JavaRanch.