Books like The Unknown Darkness
Gregg O. McCrary, Katherine Ramsland
The Unknown Darkness is 336 pages, about 6 hours 10 minutes at 250 words a minute.
12 books to read next
How long each takes
Mindhunter 7.3 h 
The Anatomy of Motive 5.9 h 
Madam Secretary 10.9 h 
The Surgeon 6.8 h 
Long Road to Mercy 7.6 h 
American Caesar 14.5 h 
Reminiscences 8.0 h 
The Fire Next Time 2.2 h 
Robert Kennedy and His Times 19.8 h 
My American Journey 11.8 h 
Velocity 8.4 h Inside the Mind of BTK 6.5 h Bar height shows length. Estimated at 250 words a minute.