In essence, JSP (Java Server Pages) do the same job as ASP and use similar, HTML-alike code to do it. At an implementation level the JSP code is converted on the fly to a Java Servlet which produces the Web page so it's no surprise to find Professional JSP covers Servlets as well.
It's been updated to cover JSP 1.2's new features--including the ability to write JSP in the language de jour, XML--and Servelet 2.3, which adds an "official" way of chaining servlets.
As Professional JSP starts with Servlets the book's title seems a little odd, but really you need both JSP and Servlets for effective J2EE presentation programming.
With 18 authors and 21 technical reviewers it's unsurprising that though technically accurate and thorough to a fault Professional JSP has a distinctly disjointed feel, often reading more like a collection of loosely related essays on the subject (which is how it probably started out) than a fully integrated guide. On the plus side, this isn't a problem if you're already a Java programmer looking to extend your skills, but it won't suit those looking specifically for a guide to JSP. Those will probably find a dedicated title such as JavaServer Pages more useful.
The real strength of Professional JSP is in demonstrating how JSP integrates with Servlets, Javabeans, XML and related technologies on the server, and how to design your server side applications to make the most appropriate use of JSP alongside these other technologies. --Steve Patient
JavaServer Pages, together with the Java Servlet, provide the dynamic web content presentation layer for the Java 2 Enterprise Edition. JSPs and Servlets integrate tightly to enable scalable and portable applications, and are widely supported. This text targets the next generation of these technologies, JSP 1.2 and Servlets 2.3, which are nearing completion under the Java Community Process and provide major enhancements to Java's web programming model. This book looks in depth at these core components of the forthcoming J 2EE 1.3 platform, preparing you for building the next generation of web solutions. You'll learn about the enhancements to the JSP tag library model; the new filtering and application event facilities; how to architect web applications to ensure a clean separation of presentation and logic; and the increasingly popular Jakarta Struts framework. The book also addresses using JSP with XML and XSLT; database access with JDBC; and how JSP and Servlets fit into the overall J2EE platform alongside Enterprise JavaBeans, JavaMail, and other J2EE technologies.