Burroughs, Edgar Rice
"Tarzan ja Oparin aarteet: Seikkailuromaani Afrikan aarniometsistä" by Edgar Rice Burroughs is a novel first published in 1916. Tarzan returns to the lost city of Opar to recover its hidden gold stockpile after suffering financial losses. A treacherous Belgian officer follows him, but an earthquake leaves Tarzan with amnesia. The high priestess La, spurned by Tarzan again, seeks revenge while Jane is kidnapped by an Arab criminal. Intrigue unfolds as multiple parties pursue Opar's treasures. (This is an automatically generated summary.)
These books are free to read. Each is in the public domain in the United States; check your own country's rules before you copy or share one.