I recommend the excellent 'proofs from the book' https://www.springer.com/gp/book/9783642008566 https://www.springer.com/gp/book/9783642008566 Containing beau

I recommend the excellent 'proofs from the book' https://www.springer.com/gp/book/9783642008566 https://www.springer.com/gp/book/9783642008566 Containing beautiful proofs (from The Book, as Erdos would have said) of sometimes elementary results.