Design Principles for a Better CMS

May be the question is so simple for you. But many times I feel it much complicated. Everyone would have started their website with a custom cms and later moved to Wordpress, Drupal, Joomla or something similar. I used to look for a better book in any language which has design decisions made for the cms to make it such a way that it can be extended. Some of the books that seems interesting to me are 1 ) Pro Zend Framework CMS 2 ) PHP 5 CMS Framework Development It will be great to see if you have came across such books or do you recommend any other books. I am not just looking for PHP, but I am interested to read any sort of books, which will help me to build the next blogger. Waiting to hear you suggestions on the same.

cmf, cms