The correspondence between Fontane and Lepel is the main source for our knowledge of the young Fontane. It contains some 410 letters written between 1844 and 1884, which give insights into social, literary and political life in Berlin. The letters have been critically edited here for the first time from the mss., and are complemented by literary and journalistic writings by the two friends. The comprehensive commentary consists of notes and explanatory indexes. The commentaries on individual passages make use of both the research literature and unpublished archive material. The afterword provides an evaluation of the significance of the correspondence.