Take a look at the table of contents and see what I mean. I can say that all of the content is carefully described and they provide diagrams illustrating the J2EE structure and code examples showing how to use each API. True to its name, it is my handbook for J2EE that I keep with me at work and on the road and so I wanted to give them a good review for a job well done. My only drawback is that the code for the J2EE 1.4 reference implementation needs to update the build scripts. But I sent an e-mail to one of the authors and he responded saying that the J2EE implementation changed and the code should work but they would send me and update their web site with the new reference implementation scritps. Since I am only using the code and the code works it was no big deal for me. I was pretty impressed that the author even responded to my e-mail since most don't.
I was kind of skeptical about it, because it promised to cover so many topics, but I was told where I bought it that I could return it within 60 days if I wasn't satisfied. So I figured it was worth a shot.
It covers everything about J2EE, and unlike the vast majority of other books, isn't a simple regurgitation of the numerous APIs. The best part is that it starts off with the core information you need, and then builds upon it. If you know a previous version of J2EE, you can easily skip to any chapter you want and learn what you need, because the core is the same, but if you're new to J2EE, you can just read it right through. Most books will discuss a topic, make a reference to another one, and give a brief explanation of the referenced topic. This makes readers, me at least, feeling a little lost, wondering exactly what's going on. Then that topic is covered 20 chapters later. This book, however, starts with the fundamentals and builds upon it. There's never a "which will be covered later" in the book.
I was afraid that the book would only skim over some topics, because it does cover the entire J2EE. However, due to the sheer size of the book (1350 content pages and another 300 pages on CD) it covers everything in detail. The only exception I think is EJBs, however anyone programming EJBs ought to pick up the O'Reilly Enterprise JavaBeans book anyway. This book covers it in enough detail that you can write and use EJBs, and gives a very thorough discussion of the lifecycle, process, and purpose, but is somewhat lacking on the configuration and advanced features of EJBs. However, like I said, it's such an extensive topic that any J2EE programmer should have the O'Reilly book in his library anyway.
The only downside to this book is that there isn't much information that an experienced Java programmer wouldn't know. This is because the enhancements to J2EE, while numerous, are not in fact new. The inclusion of web services is new to J2EE 1.4, and so is not covered in older books, but it's been so common in use that many programmers already know quite a bit about web services. Still, it gives very good information on proper usage and the interactions between web services and the other components of J2EE.
Coming away from reading this book, you're left not only with the ability to use the features of J2EE, but a solid understanding of how the components interact, what the purpose of various features are, and an incredibly thorough understanding of the workings of J2EE, something which most other books lack. The companion CD does not have any J2EE specific content, containing tools and information that further enhances your understanding of webapps (TCP/IP, HTTP, etc). I'd say this book is essential for any programmer learning J2EE 1.4, whether just new to J2EE or coming from a previous version. You're left with the ability to effectively use it, along with a thorough understanding of what's actually happening. Definitely the most used book on my shelf now.