First of all I would like to congratulate both for your book being published.
I have never used JBoss in any of my project, though I have done some small personal application on earlier JBoss version for study purpose.
Question I have is how can I put forth JBoss instead of BEA Weblogic and IBM Websphere. The reason being our Application might be eligible for move to some other server in which case it would be good to know pros and cons.
Without diving into a feature-to-feature comparison (which is a futile endeavor), JBoss AS is open source and Weblogic/Websphere are not. Being able to have a view into the development process and code is powerful. It allows you to modify, extend, and understand what's going on with the product that you're using. And if you're company needs some functionality that doesn't exist, you can always pay somebody to develop it for you and contribute it back to the project.
Also, JBoss AS has no license fees, though you can still purchase support.
From a business standpoint, I am seeing a lot of companies that have invested in applications built on older versions WebLogic Server and Websphere AS, and now that they are looking to update their applications (mainly because of support for the old app server either being dropped or getting too expensive) they are exploring moving to JBoss AS to avoid paying licensing fees. And our testing of JBoss AS has shown it is just as capable of supporting enterprise-level workloads as the proprietary products.