Future Indefinite has all the classic epic fantasy elements: a sharply detailed world of magic and gods, the struggle between good and evil, an ancient prophecy, a fish-out-of-water protagonist, a small band of adventurers, romance, love, and plenty of action. The book succeeds due to Duncan's use of these familiar elements in unfamiliar ways. Our protagonist is a young British gentleman, barely out of school; his love interest none other than his slightly horse-faced older cousin. The good vs. evil struggle is better classed as a lesser evil vs. a greater. And the prophecy? It's suitably cryptic...but also logical and quite possibly self-fulfilling.
Duncan's system of magic is not only ingenious, but integral to the book's plot. Anyone in their own world is mundane; transported to a new world (even if that world is Earth), they become 'Strangers', and gain 'Charisma', the ability to influence natives. The more people you influence, the more power you gain and the more you can influence them-- a perpetuating cycle. The competition for native followers leads to Machiavellian machinations between the Strangers in a world, some of whose powers rise to godlike levels.
One cannot read this book without drawing plot parallels to a slightly more famous book-- the Bible. Specifically Judas Iscariot's betrayal of Jesus Christ. However, the diffferences are just as significant, and any Christian who considers this book as "mocking" their faith is someone looking for a reason to be insulted.
Future Indefinite is the finale of Duncan's most serious-- and very likely his best-- series to date. Don't miss it.