After retirement in 1991, he turned to writing biographies of influential persons including Kurt Schumacher, Willy Brandt, Rudolf Augstein, and Theodor Heuss.

[3] The popular magazine, with ratings often more than 30%, covered topics such as the dark side of the "economic miracle" (Wirtschaftswunder), chancellor Willy Brandt's Ostpolitik, and the desire for social liberalisation.

[3] From 1969, he was also chief editor and head of the department of current affairs (Chefredakteur und Leiter der Hauptabteilung Zeitgeschehen) of the NDR.

He focused on biographies of persons influential in his lifetime, such as Kurt Schumacher, one of the founding fathers of postwar German democracy, Willy Brandt, the chancellor who prepared German reunification, Rudolf Augstein, the founder and publisher of Der Spiegel, and Theodor Heuss, the first Bundespräsident after World War II.

[6][8] The jury of the 2008 Leuchtturm Prize noted that Merseburger was "a meticulous researcher and courageous publicist who does not conform to the zeitgeist but always enlivens public discourse with clever arguments and interesting ideas.

With his sheer tireless creative power and analytical brilliance, Merseburger acts as a role model for independent quality journalism" ("ein akribischer Rechercheur und mutiger Publizist, der sich dem Zeitgeist nicht anpasst, sondern stets mit klugen Argumenten und interessanten Ideen den öffentlichen Diskurs belebt.

Mit seiner schier unermüdlichen Schaffenskraft und analytischen Brillianz wirkt Merseburger als Vorbild für unabhängigen Qualitätsjournalismus").