Well I think that none of us can have an opinion about this topic
We can just read books same as you do
By the way which book is it?

The strong point of the string theory is its math
The theory can explain all the known particles and force including the gravitational field
However the string theory is not supported by any lab evidences
In other words
The physicians already know what results they must achieve, thus , they , so to speak, play with the equations as long as they get what they want to get

This is the main critic to the theory and this is also the origin of the string theory

As you probably know the Maxwell's equations for the electromagnetic field and the Einstein's equations for the gravitational field are similar but not compatible

You can merge them , adding a fourth spatial dimensions
However this is just a math trick

Later . for the same reason, other dimensions have been added up to 10 spatial dimensions + time