Nothing beats a good book, whether for taking on new knowledge or having good reference material to hand. Books work without electricity, however you might still be in need of a candle.
No developing guitar builder's bookshelf should be without a copy of Melvyn's hugely popular and oft-referenced first release, "Make Your Own Electric Guitar". Melvyn's accessible no-nonsense approach on the fundamentals of solidbody luthiery is carried over into his beautifully-presented second release on the nuts and bolts of acoustic guitar building.