There are selections on the lister to use Stock Photo (if there is one for the book) and to use Gallery image. You can also use the default Title (from Product specifics) or override with your own. The Stock Photo should show as options on the Header and Gallery image selection, when available. I would always use Gallery image in US, as it's now free.
I think how many pictures and detail depends upon the book you are listing. I'm an advocate of original pictures, and the more the better. However, a simple paperback might be an overwhelm for more than a cover shot (stock photo) and good description on condition (I use IOBA standards). If you sell antiquarians, obviously pictures and details really help the sale/auction ....
View 4NinesFine: Sandburg's Abraham Lincoln
That auction FV would compete favorably with any of the majors at AbeBooks, who rarely post a picture. And, Yes, those are my original pics, description, et. al.
Danno
Edit: For some odd reason my 1st paragraph got dropped. Readded with corrections. Sorry about that!