Well talk about the book. But not like a book summary.
Ex:
Lets say there is a book called Unwanted and it's about a girl Kate, who falls in love with a guy Ren, but then the guy cheats on her with another gurl, Amy.
u dnt want to tell people a summary, more like a blurb. So i would do something like.
In the Book Unwanted, a girl named Kate falls in love with a guy named Ren. Their life is perfect, like a fairytale. Kate wishes this love could last forever. She believes she could will love him forever. But when a new girl named Amy gets in the way. Kate starts questioning her love for him. And wonders if her relationship is true love.
Something like that, hope I helped