Reading ahead for college?

So I got my books the other day and for one of my history cles there is a book about WW2. I LOVE learning about WW2, I don't know why but I find it fascinating. I was wondering if I should just read ahead. It is a 500 page book, and whether we read all of it in cl I do not know, but I think I would read it anyways? I have read a few pages, but I am afraid of being burnt out before school starts. Also by just reading it now, and skimming over the parts I underlined would I still be as successful as just reading the parts when igned?