The best language book I have ever used (and I've used quite a few) is Reading French in the Arts and Sciences (4th ed.) by Edward M. Stack. It is perfectly geared toward rapidly acquiring reading skills, with a highly effective and enjoyable method. You will not learn how to order food or read novels... all your energy will be focused on what you are trying to do, and get there quickly.
I'd say with previous knowledge of another romance language, you could within about six weeks of fairly dedicated work be reading theological articles in French and pass a dictionary-aided translation exam.
Unfortunately, it's out of print, and even used copies are pretty pricey. Maybe you can find it in a library. If not, I'd say it's worth shelling out the cash for a used copy.