In particular, the geology of Mars in an incredibly fascinating topic. If you're looking for a good primer on the subject, I highly recommend Mapping Mars by Oliver Morton.
Mapping Mars contains a history of the science, highlighting the major contributors to the field and augmented with interviews from such notable science fiction authors as Kim Stanley Robinson. A good discussion is, for example, how much water exists on the planet. Consensus is now that there is water somewhere, but exactly how much water, where it sits, how it flows: great questions that are attacked with lucid explanations.
Hats off to NASA and human curiosity for this grand adventure.