Books like Nature, Man,& Woman
Alan Watts
Nature, Man,& Woman is 209 pages, about 3 hours 50 minutes at 250 words a minute.
12 books to read next
How long each takes
Tao Te Ching 2.2 h 
Sex Matters 5.6 h 
In Defense of Purity 3.1 h 
Zhuangzi 3.5 h 
Eroticism 5.6 h 
The Sacred Prostitute 3.1 h 
Erotism 4.3 h 
I Ching 13.6 h 
The Multi-orgasmic Man 4.4 h 
Sex and Psychic Energy 2.3 h 
Chuang-tzŭ 5.6 h 
Masters and Johnson on Sex and Human Loving 11.0 h Bar height shows length. Estimated at 250 words a minute.