Books like So, What's the Difference?
Fritz Ridenour, Editor Fritz Ridenour
So, What's the Difference? is 256 pages, about 4 hours 42 minutes at 250 words a minute.
7 books to read next
How long each takes
The Kingdom of the Cults 8.1 h 
Handbook of Today's Religions / Josh McDowell & Don Stewart 10.4 h 
Living Buddha, Living Christ 4.0 h 
The Korsten Basketmakers 3.1 h 
Mankind's Search for God 7.0 h 
The World's Religions 7.9 h 
The Compact Guide to World Religions 5.0 h Bar height shows length. Estimated at 250 words a minute.