Books like Light on Prāṇāyāma
B. K. S. Iyengar
Light on Prāṇāyāma is 296 pages, about 5 hours 26 minutes at 250 words a minute.
12 books to read next
How long each takes
Science of Breath 2.6 h 
Breath 6.1 h 
Kumbhaka Paddhati of Raghuvira 3.0 h 
The Complete Yoga Book 10.1 h 
Yoga 3.8 h 
The Heart of Yoga 5.0 h 
Breathing Space 4.3 h 
Iyengar Yoga for Motherhood 9.4 h 
Yoga Anatomy 6.0 h 
Acu-Yoga 4.5 h 
Yoga Therapy 4.4 h 
Hatha Yoga 3.2 h Bar height shows length. Estimated at 250 words a minute.