Magic Key to Spanish is one of those rare books that you come back to again again, it inspires progress and there's so much to learn from it- it's certainly not going to be a dust gatherer if learning Spanish is what you truly want. If I've convinced you already buy it- if not read on.
The book starts with a very positive introduction and goes on to explain that an English speaker already knows hundreds if not thousands of words in Spanish and it gives you the rules that unlock this 'magic key' to Spanish. It then moves on to teach you grammar in a very novel way, none of the boring conjungations that had to be learnt by rote when doing languages at school. She starts with the past tense as this is how we speak to friends and then moves through much of the essential grammar required to Speak, Read and write Spanish.
I would recommend this book to all beginners in Spanish. It has got two downsides which are the layout, which is now dated (it was written in the early 1950's with Andy Warhol as the illustrator) and also (for me living in England) the fact that the emphasis is on South American Spanish not peninsular Spanish.
I wish the Magic Key to French and German were still in print as I have made substanital progress with my Spanish using this book, the method obviously works. If the publisher is reading this, please consider a reprint of the other two editions given the success of the Spanish version.
The late Margarita Madrigal was ahead of her time as the method she used in this book is akin to what trainers would now call Accerlerated Learning. A word of warning, make sure that you do all of the exercises and tests or you will not be learning to your full potential.
I recommend that you buy this book and use it in tandem with an audio course either the Pimsleur series (expensive) or Michel Thomas would be great- as these will give you the pronunciation which you will require to progress further. Both the audio courses are structured so that there is no repetition and so you have to consciously form the language and remain motivated not bored. If you would like more in-depth information on Spanish grammar I highly recommend 'Buscalo'
Hope this helps you with your introduction to the beautiful and very useful Spanish language- buena suerte!