There are many articles online and a few printed books available on the subject of Fact Oriented Modeling. When you've registered you may download an e-Book from the download section containing the original texts on FCO-IM. If you're into self-study, we recomment the book "Fact Oriented Modeling with FCO-IM". It's recently published and it's really easy to read and learn the basics.
For dutch readers the theory is available in print, and the exercises can be downloaded for free: