I am a geology major interested in groundwater modeling. Currently taking ordinary differential equations, and I'll be in a computational numerical methods course for engineers next fall. Here is the course description.. "Introduction to numerical methods for environmental engineering analysis, design and resource management using the Fortran 95 programming language." I know Fortran, so I think the next thing I need is to learn numerical methods. Some of the material for this course involves error analysis with bounds, and the Runge-Kutta method. Does anyone know of a good book that would introduce me to numerical methods?