Soren Kierkegaard 
Provocations [PDF ebook] 
Spiritual Writings of Kierkegaard

Provocations contains a little of everything from Kierkegaard’s prodigious output: his famously cantankerous (yet wryly humorous) attacks on what he calls the "mediocre shell" of conventional Christianity, his brilliantly pithy parables, his wise (and witty) sayings. Most significantly, it brings to a new generation a man whose writings pare away the fluff of modern spirituality to reveal the basics of the Christ-centered life: decisiveness, obedience, and recognition of the truth.