The followers of Muhammad are often a mystery to most Catholics. This is why I wrote A Catholic’s introduction to Islam, which will explain the basics of Islam. I’m currently read the Qur’an cover-to-cover and my notes are available here. and building up a glossary for Islam.
I don’t have too many apologetics pieces on Islam yet, but I have written a response to the classic Muslim Denial of the Crucifixion, as well as another responding to the consternation of Muslims concerning Jesus’ apparent ignorance of figs. Many more articles will be coming in 2017.