The 20th Century Limited's more affordable train car was known as "Tavern Lounge No. 43." Here, coach passengers could socialize and hang out in a space separate from their assigned seats.

There is some hubris in daring to define the key features of a century’s worth of novels, but Edwin Frank admits his book isn’t — and indeed can’t be — comprehensive.

Between the hot war in Europe and a brewing cold one between America and China, today’s world has a very 20th-century feel. Amid these echoes, historians and international-relations buffs have ...