Lerman was born in Požega, Slavonia, but he left his home very early.

The first, published in 1891 under the title Dnevnik iz Afrike (Diary from Africa), was written and printed by his friend from Požega, Julije Kempf, whom Lerman informed about the course of the exploration.

The second one was published in 1894 with the title Novi dnevnik iz Afrike (New diary from Africa).

Lerman provided inspiration for two additional explorers (Mirko and Stjepan Seljan) who were mapping Africa and South America at the turn of the 20th century.

His original diary is in the archives of the Croatian Academy of Sciences and Arts.