In 1879 he released the travel guide Reisehaandbog over Norge, popularly called Yngvar, which appeared in 12 editions until 1915 and came to play an important role in the spread of tourism. His guide books were published in English and German.
In 1879 he published the travel manual Yngvar, also known as Reisehaandbog over Norge, which ran in 12 editions until 1915 and played a significant part in promoting tourism. His guidebooks were released in English and German.