April Wilson's German Quickly is an exceptional book for learning German on your own. A peer of mine studied over the summer before his 1st year using that book and some vocabulary flashcards and passed his German language proficiency exam that Fall. I will be doing the same this summer if anyone is interested in also getting the book and perhaps having some sort of online reading circle. Part of the reading circle could be communicating in German, which I personally believe is important for understanding.
AnonymousMonad- My thought would be that a knowledge of "language-for-living", as you say, would help one maintain their understanding of sentence structure and grammar. Having to construct one's own sentences in dialogue is wonderful practice. Also- if one is serious about wanting to study German texts, it would be nice to be able to speak the language with those you might be in contact with when trying to hunt down documents! Personally, I would love to do some work with the Husserl archives in the future, and am maintaining my speaking knowledge of Dutch for that purpose. It is much easier to navigate Flanders when you speak Dutch.