The Croats are Catholics. The Muslims in Bosnia, they are Slavs (Croats and Serbs) converted by the Turks.
Nobel Prize winning author Ivo Andric was a Bosnian Croat by birth (although he lived the latter decades of his life in Belgrade). His novel The Bridge on the Drina does a good job of depicting the different groups in Bosnia under Turkish rule. It is structured like one of James Michener's historical novels, jumping from one historical period to another but staying focused on the same town in Bosnia.