Die Welträtsel (1899; in English: The Riddle of the Universe, 1901) is a non-fiction book by biologist and philosopher Ernst Haeckel (1834–1919). Best known for his Kunstformen der Natur (“Art Forms of Nature”), Haeckel promoted and popularised Charles Darwin’s theory of evolution in Germany.
The typeface used on the cover of this “newly revised pocket edition” from 1909 is König-Antiqua, designed by Heinz König and first cast by the Klingspor foundry in 1905. Note the use of the ſ (long s) in roman type. The KTA monogram (for Körners Taschenausgabe) is custom lettering with similarities to Eckmann. The title page shown below is set in Mainzer Fraktur (Berthold, 1901).