In one world, he’s the cel­e­brated author of The War of Art—a book that has quickly become the field man­ual for any­one engaged in cre­ative or artis­tic work of any kind, espe­cially entre­pre­neurs and writ­ers. In the other world he’s the king of all mil­i­tary epics and his­tor­i­cal sagas — a think­ing man’s Tom Clancy whose nov­els about The Bat­tle of Ther­mopy­lae, Alexan­der the Great, and The Pelo­pon­ness­ian War are favorites among grunts, gen­er­als, and lit­er­ary crit­ics alike. Unfor­tu­nately, there’s not nearly enough cross pol­li­na­tion between the two worlds. Few of Steven’s fic­tion fans have read his non-fiction, and even…