He rose to early fame as the editor of several anthologies of German poetry of a spiritual kind, including Der deutsche Psalter and two volumes of Die Ernte aus acht Jahrhunderten deutscher Lyrik, and for his retelling of the Tristan and Isolde and Parzifal legends, all of which sold in tens of thousands before 1914.
In these he displayed a decidedly nationalistic perception, which together with his glorification and exalting of the love of the native soil, of motherhood and war, made it inevitable that he would become a representative of Nazi ideology.
His best-known work Das harte Geschlecht, about the Christian conversion of Iceland, appeared in 1931, and in May 1933 was praised in the Völkischer Beobachter as a "thoroughly bloodthirsty Northland novel".
In his literary Journal Die Neue Literatur Vesper carried out a kind of private censorship or revisionism, regularly embarking upon defamatory campaigns against authors and publishers who did not agree with his personal views.
By 1936, he withdrew from his duties to the estate of his wife Rose (Rimpau) Vesper at Triangel bei Gifhorn, where he occupied himself as a farmer but also continued to issue his literary newsletters until the year 1943.