I know the title looks vague and the concept also looked strange to me when I read this.
In the image , it is pretty clearly written that to avoid skiding friction force serves as the centripetal force. But just a line below, the equation says :
$$Centripetal\; \;force≤Force \; \; of \; \;friction $$
I don't know if it is true but I don't think it is true. If friction is the only horizontal force here then why should it be smaller than centripetal force ?
I would like to add that this book claims to be errorless and it is the name of this book. Also correctCorrect me if I am wrong somewhere.