If this sequel—["The Old Patagonian Express"] must be called that—is not so delightful as "The Great Railway Bazaar," the fault is as much geography's as Theroux's. Europe and Asia are a richer venue for this sort of thing than Latin America, which by contrast lacks character, deep literary and historical associations, and variety. For anyone experienced with Europe, it is desperately boring. Squalor in Mexico is identical to squalor in El Salvador; the ghastly Mexican town Papaloapán is too much like the horrible Costa Rican town Limón, 600 miles farther south. Illiteracy here is like illiteracy there. As Theroux proceeds, things do get worse, but not dramatically worse: "Since leaving the United States," he writes, "I had not seen a dog that wasn't lame, or a woman who wasn't carrying something…." He seems aware that his sequel isn't quite up to the original, alluding to...