For those who self publish as I have done using Blurb or similar on line services.
I received some very useful advice from Jerry D Simmonds at
Nothing Binding , who has a great many years of experience working at the very top in the publishing industry.
Effectively the advice as I see it is;-
When marketing your work using on line preview pages to display book content, only supply enough to entice a potential purchaser's interest. On the basis that if you show a full preview, your whole work is accordingly available on line, reducing the books potential and effectively, your sales may suffer accordingly.
Good luck