Because Servlets and JSP isn't a topic you can fully grasp when you read the first time about it I found it useful to read several books about this topic: My first book was also the one from O'Reilly ("Java Servlet Programming"), then i read "Core Servlets and JSP" from Sun and "Advanced Java Server Pages" also from Sun. Recently i also borrowed "Web Development with Java Server Pages" from Manning Publishing.
I have to say, that there are many books for java and advanced java books out there and - gladly - nearly every book is worth a read. Expecially O'Reilly, Sun and Wrox books are really good. You could buy any of them without having to consult book reviews.
Since you already have a good understanding (with the stuff you read) i'd definitly recommend you "Advanced Java Server Pages" (ISBN: 0130307041), which introduces you into some advanced topics and some design aspects of servlet and jsp programming. The topics covered there show you, how servlets and jsp are (or how they can be) actually applied in business.
A second title i can recommend you is "Core
J2EE Patterns".
/JT