I bought Budi's newest book because I liked the style of his earlier book on JavaServer Faces. He has an ability that is rare for most technical authors...He can make a very complex topic understandable.
Although Tomcat is pretty easy to set up and use as a developer, to really understand the internals of the server one must wade through thousands of lines of code and even then it can be a daunting task. Furthermore, understanding the "how" is only half the battle. To really gain an understanding of the server, one must understand "why" the Jakarta folks did things the way they did.
Budi (and Paul Deck) did a great job of not just giving a code review of the server, but also describing the reasons why the server is constructed the way it is.
Having written a few Tomcat Components the hard way - trial and error - I can say the insights given in this book have helped a great deal.
But, as I say in the title, this book is not for the squeemish. There is a sizable amount of fairly complex code. To really understand the point of the book, the reader must be VERY familiar with the Java language, Java Web Applications, TCP/IP, and be willing to ponder a code listing for a while to really understand it. In other words, this is not what I would call a "passive read".
If you have the basic understanding necessary, this book will shed a great deal of light on one of the darker corners of server-side Java development.
This is great read for anybody wanting to really understand the internals of Tomcat.