This is the 2097th most frequent Turkish word.
üzeri
"Üzeri" means "on top of" or "above" in English.
Here 'üzerinde' indicates a physical position, 'on top of', relative to the book.
Kitabın üzerinde bir kalem var.
There is a pen on top of the book.
In this context, 'üzerinde' refers to something being on the surface or exterior of an object.
Yüzeyin üzerinde ufak çizikler gördüm.
I saw small scratches on the surface.
Here 'üzerinde' is used figuratively to mean 'above a certain amount or level', in this case, a percentage.