Books like Diary of a 6Th Grade Ninja
Marcus Emerson, Sal Hunter, Noah Child
Diary of a 6Th Grade Ninja is 104 pages, about 1 hour 54 minutes at 250 words a minute.
6 books to read next
How long each takes
Young Samurai 7.9 h 
My Pants Are Haunted (Dear Dumb Diary #2) 2.3 h 
Never Underestimate Your Dumbness 2.8 h 
The Problem with Here Is That It's Where I'm From 2.4 h 
The Worst Things In Life Are Also Free 2.7 h 
Am I the Princess or the Frog? 2.7 h Bar height shows length. Estimated at 250 words a minute.