Here are two excellent books for learning Latin.
John Collins' grammar is, in my opinion, the best introductory grammar out there. I wish I had it used to teach myself Latin instead of Wheelock. It's the perfect book to get started with. Finishing this book will give you enough grammar to begin reading your Vulgate. Each lesson builds on the previous one, and new words and concepts are introduced in small doses. As a result, you will never feel overwhelmed by your studies. Once you get the basic grammar down, then you're ready to move on to Latin texts. Tonight I'm reading Augustine's Confessions. This diglot edition has the English and the Latin texts on facing pages. I focus on reading one paragraph at a time and mastering the grammar and vocabulary before going on. For the most part, the translator did a good job of rendering the Latin, though I often find myself wishing he had a bit more literal.
I would highly recommend both books.