Books like Understand the Unknown
K. A. Applegate
Understand the Unknown is 179 pages, about 3 hours 17 minutes at 250 words a minute.
12 books to read next
How long each takes
Shatter Me 6.8 h 
The Little Prince 1.8 h 
A Court of Thorns and Roses 8.3 h 
Unravel Me 8.5 h 
A Wrinkle in Time 3.9 h 
Ignite Me 7.6 h 
Restore Me 8.1 h 
Crown of Midnight 8.2 h 
Six of Crows 9.4 h 
Heartless 9.4 h 
The One 5.9 h 
Red Queen 8.1 h Bar height shows length. Estimated at 250 words a minute.