My first thought when I learned that this year’s National Book Festival was moving from the Mall to the Walter E. Washington Convention Center was of the Morlocks — those pale underground creatures from “The Time Machine,” H.G. Wells’s take on our distant, bifurcated future. In his vision of the year 802,701, one half of humanity, the Morlocks, dwells in dark caverns beneath the earth, tending to “the machines” and feeding off the other half, the beautiful and stupid Eloi, who graze and gambol in the garden above.