I am writing a calculus textbook called Calculus Illustrated. In addition to the standard material, it presents discrete calculus, something every scientist should be familiar with. $$\lim_{\Delta x\to 0}\big( \begin{array}{cc}\text{ discrete }\\ \text{ calculus }\end{array} \big)= \text{ calculus }$$

My first book was Topology Illustrated. Section 1.1 Topology Around Us contains what in my opinion every scientist should know about this discipline.