I am reading these geography books right now:

Duckham, Matt, Goodchild, Michael F. & Worboys Michael F. Eds. Foundations of Geographic Information Science (London: Taylor & Francis, 2003).

I just started this book and have not gotten far with it. I read the basic attempts at defining geographic information sciences.

Rushton, K.R. Groundwater Hydrology: Conceptual and Computational Models (Chichester, West Sussex, England: Wiley, 2003).

With this book I have just read the introductory chapter and then followed the author's suggestions for novices to scan the book. It is very complex math and uses case studies. The math though is not beyond me and it uses only math I can understand with my B.Math degree as far as I can see by the diagrams and cross sections.

That's it for geography books I am reading right now.