Multi variable calculus would be helpful too, I found to be able to compensate using a search engine. A decent understanding of trigonometry and single variable calculus are mandatory prerequisites. The author builds the way up from geometric considerations to eventually deriving the div, grad, curl and laplacian operators of vector calculus (hence the title).
For single variable calculus, I went through Calculus Made Easy (by Silvanus Thompson) Div grad curl was an incredible experience to me. Div grad curl was an incredible experience to me.