Encyclopedia of Mathematics? (non-alphabetical) Do you know any encyclopedia of mathematics which is in non-alphabetical order, like it starts from basic mathematics and then goes up to very advanced level?
And what's the difference between say, if I am studying calculus from a mathematical encyclopedia and if I am studying calculus from a university based calculus textbook?

You might be interested in Mathematics 1001: Absolutely Everything That Matters About Mathematics in 1001 Bite-Sized Explanations by Richard Elwes (Firefly Books, 2010).
The author's website is here.  A review can be found here.  I have a copy of it and it's extremely good.  A high school student will be able to understand the first few paragraphs of each topic, and a smart undergraduate student will be able to understand the most difficult parts.
