Only 12 days in your hectic schedule - that is all you need to allot in order to become an efficient Spanish speaker or conversationalist. You don't believe it?
First of all, I am aware of the fact that people's lives are getting busier and busier everyday. We are forced to fit tons of activities in a day. Sometimes there's no time left for ourselves.
Time is indeed essential to most of us. The fact that you're canvassing Spanish books in the internet means you have no time to go to any bookstore or library to acquire one. You may want to do things in the least possible time, using the easiest and most effective ways, in order to make the most out of your busy schedules.