Books like Discovering Chess Openings
John Emms
Discovering Chess Openings is 174 pages, about 3 hours 11 minutes at 250 words a minute.
6 books to read next
How long each takes
Modern Chess Openings 8.4 h 
Batsford Chess Openings 6.3 h 
Chess Openings for Dummies 7.1 h 
Chess Openings 4.7 h 
The Art of Defence in Chess 4.9 h 
The Complete Book of Chess Strategy 6.6 h Bar height shows length. Estimated at 250 words a minute.