Marsbound, Joe Haldeman’s latest novel, starts slowly and intimately: the first quarter of the novel is spent following his young protagonist, Carmen Dula, and her family on a weeks-long trip up a space elevator and thence on their journey to Mars. The second quarter unfolds like a Heinlein juvenile (except for the sex), with Carmen’s struggle to survive on Mars personified by a stern and bureaucratic authority figure with whom she comes into conflict. Once Carmen runs away and stumbles upon a colony of Martians, however, the similarities to, say, Red Planet end. The novel pivots, draws back in scope and dramatically accelerates its pace; years fly by in the same number of pages that described hours, as Carmen returns to Earth orbit with a posse of Martians — who turn out not to be indigenous to Mars and unsure of their own origins — as they try to figure out where they come from. Marsbound finishes as another iteration on a common Haldeman theme: human beings facing the judgment of overwhelmingly powerful aliens. The Martians and other aliens are wonderfully imagined in this otherwise spare novel, whose two halves never quite fuse into a satisfactory whole.