I am asking this question because of Zend Framework. I really like it but still the way it offers modularity is not really flexible. For instance a lot of us at first create default and admin module , but in reality it is not reusable. In fact admin should be not a module but some paradigm that takes care of every single module's admin side (like a plug-in manager).
So, anyhow, is there are Good book on Architecture of Modular Web Application?
P.S. sorry if this is a duplicate.