Forget books. The best way to learn a language on one's own that I know of is Pimsleur language sets. They're costly--about $600 for the complete 3 sets of tapes, but well worth it, and you can sell them back on ebay once you're done with them. They'll take you to intermediate level in about 3 months, from which point you can augment your Spanish fairly easily. Cheaper than immersion courses. It's the way to go, imo.