This book should not be in Science, except possibly as an example of how far medical science has progressed from the time of this book (1911). The book is basically a warning to young Christian men to not masturbate or have sex before marriage, and to only have sex a couple times a month at most after marriage. Oh yeah, and also to not have sex with your wife for one year after first learning she is pregnant.
The author tries to give sciencey-sounding reasons for the above, but almost nothing is traceable to actual medical science, instead it is all based on (flawed) arguments of one type or another, typically arguments from authority. It is full of very out-dated assumptions about 'the fairer sex' and marriage.
Some of his 'facts' are just plain wrong, for example he thinks women are most likely to get pregnant either just before or just after menstruation, when in fact it is closer to the opposite-- loosely speaking, pregnancy is most likely if coitus occurs during ovulation, which is typically at the opposite end of the cycle (approx. 2 weeks after/before her 'period').