A few months ago I was given the opportunity to write for the german "Java Magazin". They asked for an article on the popular Apache OFBiz - the first level ERP system by the Apache Software Foundation I am such a big fan of. Being an avid reader myself I was smitten.
The article I ended up writing gives a basic overview over the material at hand, gives short code examples to the most interesting aspects of the software and also analyses the pros and cons quite a bit. So if you have been looking for a great open-source business solution, perhaps you should check the article. Of course it is also available at your local bookstore.