I thing that if you are the sort of person that really likes design patterns, the sort of applied category-theory that the likes of Erik Meijer, Bartosz Milewsk

I thing that if you are the sort of person that really likes design patterns, the sort of applied category-theory that the likes of Erik Meijer, Bartosz Milewski, Rúnar Bjarnason or Gabriel Gonzalez talk about is actually a good next step after the GOF Desing Patterns :-)