These books present calculus, fluid motion, and problem solving in accessible ways.
Cipra, Barry. Misteaks [sic] and How to Find Them Before the Teacher Does. 3rd ed. Wellesley, MA: A. K. Peters, Ltd., 2000. ISBN: 9781568811222.
Pólya, George. Mathematics and Plausible Reasoning. 2 vols. Princeton, NJ: Princeton University Press, 1990. ISBN: 9780691025094 (v. 1) and 9780691025100 (v. 2).
———. Mathematical Discovery: On Understanding, Learning, and Teaching Problem Solving. Combined ed. New York, NY: Wiley, 1981. ISBN: 9780471089759.
Schey, H. M. Div, Grad, Curl, and All That: An Informal Text on Vector Calculus. 4th ed. New York, NY: W.W. Norton, 2005. ISBN: 9780393925166.
Van Dyke, Milton. An Album of Fluid Motion. Stanford, CA: Parabolic Press, 1982. ISBN: 9780915760022.