The Concept of Anxiety
All of Kierkegaard's books have either a preface, dedication, or prayer at the beginning. This book includes a lengthy introduction. "The Concept of Anxiety" was published on exactly the same date as "Prefaces", June 17, 1844. Both books deal with Hegel’s idea of mediation. Mediation is a common thread throughout Kierkegaard’s works. His work up to this point was to show that faith was being mediated by knowledge. Here he takes up the questions of sin and guilt.
Prefaces
Kierkegaard contrasted one fictional author with another frequently. This book and its companion piece, "The Concept of Anxiety", contrasts Notabene, who is mediated by his wife as well as his reviewer, with Haufniensis, who is against his knowledge of sin being mediated by Adam.