Oft-recommended series of 10 letters.  Although you can find much of this creative and life advice scattered throughout the self-help world, Rilke communicates big ideas with few words.  This early 1900s classic strikes such a modern tone and keeps its classic appeal through Rilke's uniquely earnest, thoughtful, and gentle words, with a few vulnerable moments sharing his own personal struggles with loneliness, self-doubt, sadness and the like.