How to integrate WP with my own PHP/MySQL CMS

I have developed a CMS that contains hundreds of books, articles, and audio lectures but want to integrate it with WP so I can make use of the beautiful themes and powerful plugins but without keying in the same information that I have already entered into my CMS database. I have explored the use of Advanced Data Types plugin but not sure if it is the most suitable plugin for this kind of work. Any pointers specially from those who implemented an integration between WP and their custom built CMS would be greatly appreciated.
Thanks,