...and there's some more information, including a summary of the contents and some sample chapters at
http://www.projsptags.com.
As far as how it differs from the other tag books that's an excellent question. I wanted to provide insights into how to build tags from several different perspectives. First of all there is the usual "this is what is available, and this is how you use it" that demonstrates real world examples of basic tags, tags with attributes, iteration tags, body tags, cooperating tags, tags that introduce scripting variables and so on. In addition to this are the other facets of custom tag development that you don't often find covered such as validation with TagExtraInfo classes, validation with TagLibraryValidator classes and so on.
Something that I really wanted to cover alongside all of this stuff was best practices. For example, there are many ways in which tags can cooperate (e.g. using variables, directly, etc) so included in the text are various recommendations about when to use which mechanism, and the scenarios in which that mechanism can best be applied. Of course this is just one example and the best practices are part of every chapter.
The other aspect that makes my book different is that it has a couple of chapters dedicated to the best development techniques that span different types of tags. This covers low level issues such as tag pooling in the container and how to best make use of the tag lifecycle, to higher level issues such as how OO and component based development maps onto JSPs and custom tags, and a detailed comparison of JavaBeans vs. custom tags that brings to the forefront the issues around reusability and maintainability.
In essence, I wanted to write a book that dealt with as many of the custom tag features as possible, allowing anybody to start writing reusable, maintainable components.
Do take a look at the website and feel free to fire away with anymore questions you may have.
Simon
[ September 11, 2002: Message edited by: Simon Brown ]