This Is The Only Kingdom by Jaquira Díaz

Jules is a young man barely a century old. He's lived long enough to see the cure for death and the end of scarcity, to learn ten languages and compose three symphonies…and to realize his boyhood dream of taking up residence in Disney World. Disney World! The greatest artistic achievement of the long-ago twentieth century. Now in the keeping of a network of "ad-hocs" who keep the classic attractions running as they always have, enhanced with only the smallest high-tech touches. Now, though, the "ad hocs" are under attack. A new group has taken over the Hall of the Presidents and it appears this new group has had Jules killed. This upsets him. (It's only his fourth death and revival, after all.) Now it's war….