Just started reading this book by Zubrin. It is not exactly "the case for mars", in that it does not dedicate the entire book to planning for specific missions. What it does do is carefully examine the possible human future in space. It also, perhaps most importantly, dismantles and refutes all of the silly notions about space exploration being propelled by asteroid mining, space tourism, space power generation, or other fantasies. Zubrin knows these plans for what they are, at best unrealistic plans akin to extracting gold from the Ocean, and at worst, just one more way to justify the lack of government investment in the space frontier.