I've seen a few people recommend The Princeton Companion to Mathematics(PCM) http://press.princeton.edu/titles/8350 I own this book and while I do agree it's a great book for getting a 10000 foot view about topics in mathematics it's not really a book one read to learn the math that the poster is asking for. I agree with another post here that said studying is doing problems and being able to do them again a week later without having to consult the text again. PCM isnt a good book for learning calculus, discrete math, probability or statistics( what the posters wants to learn) simply because it isn't designed to teach them. There are no problems/solutions in the book to try. If you really want one book then I'd recommend Concrete Mathamatics http://www.amazon.com/Concrete-Mathematics-Foundation-Comput... (http://www.amazon.com/Concrete-Mathematics-Foundation-Computer-Science/dp/0201558025/ref=sr_1_1?ie=UTF8&s=books&qid=1245423997&sr=1-1) by Graham, Knuth and Patashnik. It has relevant topics and problem sets that you can work through to see if you truly did learn anything when reading it.
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