Divine Comedy is one of the toughest books in western literature canon. There’re 3 points I want you to know before you begin this book.

1.It’s a fantasy. Dante never claimed it’s true in any way.

2.The work reflects the medieval world view and Dante’s personal understanding of the faith. It’s NOT the teaching of the medieval Holy Church in any way.

3.Dante wrote this work while he was in exile. He had strong opinions about Politics in Florence which he could not find a place to express. So he hid many Political references inside the Comedy. You had to know the political affairs of Florence to fully appreciate the work. (another book famous for this is St Thomas More’s Utopia)

With that said, the best book still in print for 1st time Divine Comedy reader is (in my opinion):

A Modern Reader's Guide to Dante's the Divine Comedy
By Fr. Joseph Gallagher

BTW: I am in US.