Proofs from THE BOOK
Martin Aigner, Günter M. Ziegler, Karl H. Hofmann
My French Professors in France always demanded rigourous proof from us, but never emphasized elegance is equally important, if not more.
I like the short and elegant proofs in the side-bar window-box, e.g. Lagrange Theorem on subgroup, etc.
To say it to be understood by High School or undergraduate students is a bit exagerated. Frankly, some of the proofs are quite complex and abstract, I think they are at Masters level.
I recommend it to be in any library or home bookshelf.
