The Summa of St Thomas Aquinas. I once got all the way to page 22 in this; I am hoping to do better this time before giving up.
The House of the Seven gables by Nathaniel Hawthorne. I get in the mood to read Gothic-y books like this when autumn, October, and my favorite holiday rolls around...I'll probably start All Hallows' Eve by Charles Williams when I finish the Hawthorne book.
Good Lord, don't try to read that like a novel. It's good for reference material and there are online collections with search engines. I recently purchased the entire Aquinas collection that has been translated into English on CD which also includes a search engine and other bells and whistles. Also, I think it would be difficult to understand the Summa Theologica (I'm assuming you are not referring to Summa Contra Gentiles) without a firm grounding in Aristotle.