NOMINALLY, LYDIA MILLET’S TWELFTH NOVEL, Dinosaurs, takes its title from the birds that inhabit the Arizona desert in which the book is set. But it also refers to Millet’s protagonist Gil, a kind, aimless man in his mid-forties. Orphaned in early childhood, he inherited a fortune at age eighteen and, when we meet him, is both ashamed of being “disgustingly rich” and fixated on finding the single “best way to contribute.” He’s so terrified of doing wrong that he’s spent his adulthood doing little but clinging to an unhappy relationship, volunteering at a series of nonprofits, and yearning to be