I got decent grades in college Spanish; two “A-‘s” and a “B+.” However, when I needed to actually speak Spanish, I was lost. I couldn’t say much except “Mas cervezas, por favor (More beer, please)!”
"Madrial’s Magic Key", along with the expensive (but quite worth it) Pimsleur tapes, have corrected the “mis-education” I was subjected to. The drills Ms. Madrigal presents are easy to remember and fun to do, not like those tedious translations and verb conjugations that college texts are so fond of. In two months, studying this book in my spare time, I retained more Spanish than I did in an entire academic year. And, for the first time, I can actually say that I understand Spanish.
I would supplement this book with a comprehensive book on Spanish grammar (I have the Barron’s, but I suppose any would work) and a dictionary. I would definitely recommend “Breaking Out of Beginner’s Spanish” by Joseph Keenan for an in depth take on colloquial Spanish as well. Further, if you have the money, buy the "Pimsleur Comprehensive" series as well. Get vol.’s 1-3, even though they are pricey. If you are an audio/tactile learner like me, I guarantee that you will retain more Spanish idioms using the Pimsleur method than any other.