Books like The Mystery of the Purple Pool
Gertrude Chandler Warner, Charles Tang
The Mystery of the Purple Pool is 125 pages, about 2 hours 18 minutes at 250 words a minute.
12 books to read next
How long each takes
The Bad Beginning 3.2 h 
Sisters 3.6 h 
The End 6.8 h 
The Grim Grotto 5.9 h 
Into the Gauntlet 5.7 h 
Double Fudge 3.9 h 
Tales of a Fourth Grade Nothing 2.2 h 
The Black Book of Buried Secrets 3.4 h 
A Family Apart 3.0 h 
Dark Places 6.8 h 
The Maze of Bones 4.1 h 
The Viper's Nest 3.2 h Bar height shows length. Estimated at 250 words a minute.