At this point, I have the basic psychology books, some other recommended and optional books, G's books, the Hervey Cleckly book and several other pdf's that are available. I've also downloaded and compiled into an ebook, the Online Wave, Adventure Series, all the QFG-related psychopathology studies, as well as all my posts (as a single-point source of all the reference material I've ever posted).
I think that's more than enough for me. If the 'net' goes down, I think I'd be more concerned with the inability to communicate with others, than having access to written info, but maybe that's just me.
I do think it's a good idea to save anything you don't have fully understood yet, though, but you could also just download HTML pages, organize the material in properly-named folders, then use your Operating System's search function on a folder to find what you need, OSIT.