Zecharia Sitchin books in order
14 books in the catalogue, about 82 hours of reading in all; the shortest takes 3 hours and the longest 8 hours.
1 series and 8 standalone books in the catalogue.
Earth Chronicles
7 books
The 12th Planet 7.0 h 
The Stairway to Heaven 6.0 h 
The Wars of Gods and Men 6.9 h 
The Lost Realms 5.5 h 
When Time Began 7.5 h 
The Cosmic Code 5.6 h The End of Days: Armageddon and Prophecies of the Return length not known
