The force of static friction acts  upward from the wall on the book.

静摩擦力从墙壁向上作用于书本。

And the maximum force of static friction is just equal to the coefficient of static friction times the normal force.

最大静摩擦力为 静摩擦力乘以法向力的程度。

That means there is an equal but opposite force of static  friction which acts downward from the book on the wall.

这意味着存在一个大小相等但方向相反的静摩擦力，它从书本向下作用于墙壁。

The equation then is the force of static  friction is less than or equal to the coefficient of static friction times the force normal.

那么方程就是静摩擦力小于或等于静摩擦系数乘以法向力。

What  happens then is that the force of static friction adjusts in an attempt to keep the two surfaces  from sliding relative to one another.

接下来会发生的是，静摩擦力进行调整，以防止两个表面相对滑动。

The maximum force of static friction which would prevent an object from sliding  on a surface is the force of static friction maximum equals the coefficient of static friction  times the force normal.

阻止物体在表面滑动的最大静摩擦力是静摩擦力最大值等于静摩擦系数乘以法向力。