[I was advised] to read Jordan's 'Cours d'analyse';....

“ [I was advised] to read Jordan's 'Cours d'analyse'; and I shall never forget the astonishment with which I read that remarkable work, the first inspiration for so many mathematicians of my generation, and learnt for the first time as I read it what mathematics really meant. ”

G.H. Hardy

From : A Mathematician's Apology