Books like DOS for Dummies
Dan Gookin
DOS for Dummies is 320 pages, about 5 hours 52 minutes at 250 words a minute.
6 books to read next
How long each takes
DOS Internals 13.5 h 
DOS 16.9 h 
Advanced MS DOS Programming 10.4 h 
The Cathedral and the Bazaar 4.7 h 
Terraform : Up & Running 5.3 h 
Undocumented DOS 15.2 h Bar height shows length. Estimated at 250 words a minute.