Why There Are Pages and Why They Must Turn, by our personal hero, the poet and typographer Robert Bringhurst. If it gets you misty-eyed you can buy the letterpressed and handbound version (printed by Peter Koch, who is a legend in his own right) of this essay here If you haven't read The Elements of Typographic Style you should probably do that too. It is not so much a guide to book design as it is a meditation on the necessity of making beautiful things. It will change your life. We're not joking.