I've read the Quran annually (a well as the Bible and Catechism) for a number of years now.  Was stationed in the Middle East in the late 70s and traveled widely while I was there. 

The Quran reminds me of the Old Testament prophetic books and the writings attributed to Paul in tone and content.  Islam,  like the Jehovah's Witnesses, seemed to me to be branches of Arianism. Since they believe in Jesus,  and teach charity,  almsgiving and mercy, I considered them to be a branch of Christianity. 

The problem is, even Christians can't agree on who Jesus is, Mormons (who share with Islam the adding of books to the Bible) and Protestants (who have taken books out of the Bible) will tell you how wrong Catholics are (to them) and vice versa.