The PDF documentation covers the 2.4.x version.
Overall the information is relevant to 3.0, but of course there are many new and changing areas that are not covered.
Does that mean that the book covers the 2.4 version as well?
Yes, the book cover jboss-2.4.4 as the downloadable documentation does today.
If you are deploying applications with jboss-3.0 there are some new things to deal with:
a) jetty-4.0 is integrated, that does not mean that you can not use other servlet deployer.
b) as jboss-3.0 is evolving the directory structure had change a bit.
c)jetty-4.0 recomends to use only some of his jetty-3.0 options leaving to jboss-3.0 the deployment tasks.