A number of traveler's accounts and works of early scholarship on Persepolis are beginning to emerge in open access formats at the Internet Archive. Among these are:
Travels in Assyria, Media and Persia : including a journey from Bagdad by Mount Zagros, to Hamadan, the ancient Ecbatana, researches in Ispahan and the ruins of persepolis (Volume 1) - Buckingham, James Silk, 1786-1855
Travels in Assyria, Media and Persia : including a journey from Bagdad by Mount Zagros, to Hamadan, the ancient Ecbatana, researches in Ispahan and the ruins of persepolis (Volume 2) - Buckingham, James Silk, 1786-1855
Nineveh and Persepolis : an historical sketch of ancient Assyria and Persia, with an account of the recent researches in those countries - Vaux, William Sandys Wright, 1818-1885
Narrative of a residence in Koordistan : and on the site of ancient Nineveh; with journal of a voyage down the Tigris to Bagdad and an account of a visit to Shirauz and Persepolis (Volume 1) - Rich, Cladius James, 1787-1820
Observations made on a tour from Bengal to Persia, in the years 1786-7; with a short account of the remains of the celebrated palace of Persepolis and other interesting events - Francklin, William, 1763-1839
Remains of lost empires: sketches of the ruins of Palmyra, Nineveh, Babylon, and Persepolis, with some notes on India and the Cashmerian Himalayas - Myers, P. V. N. (Philip Van Ness), 1846-1937