Play it if: you wish for a game that explores puzzles of dialogue and discourse, or if you want to hear a powerful, emotionally resonant variation on the tale of Gilgamesh.
Don't play it if: you have trouble with puzzles that depend on intuition rather than pure logic, for it is as often as not by intuition that you progress through the story.
There are two reasons I love this story.
The first is intuition. The "puzzle" of the game, if it can be truly called a puzzle, is one of persuasion: to win the people of your tribe over to your way of thinking by directing the flow of a story. The player does this primarily by interacting with emphasized terms in the telling. Where intuition comes in is that you have no control over precisely what to do with each term; it is on the basis of each word's context in the story that you must decide how to interact.
This means that, to perhaps the greatest degree possible in IF, this is a game about language, a game which emphasizes reading comprehension over puzzle-solving. Not only is this fairly unusual for the genre, it is excellently done - the player can deduce important lessons even from minor details in the telling.
The second is the story itself. The storyteller narrates the first half of the Epic of Gilgamesh, the oldest written epic in recorded history and a myth which still resonates with and influences modern literature. The choice of story is perfectly suited to this work, for the Epic is primarily about fear - in particular, fear of death, and fear of the unknown - and the search for immortality, whether through glory or through the love and friendship of others. These are powerful themes that the framing narrative explores, taking place on the eve of tribal war.
Whom the Telling Changed is itself an allegory of the Gilgamesh story, and in adding another fundamental theme - the power of legend and narrative - Aaron A. Reed succeeds in crafting a myth of his own. This is fantasy from an older and darker time, from a world where life was brief and difficult. For many people in those times, the only spiritual and moral comfort to be offered came from the telling and understanding of old stories - as Reed understood when he tapped into that primordial image of a troubled tribe gathered in darkness around a warm campfire.
There are but a few other notes I have on this work. There are one or two glitches to be ironed out - I only ran into one of them, though, which given the game's NPC interactions is a pleasant surprise. Also, while in general I'm no fan of sequels, there is another chapter to the Gilgamesh myth...perhaps there is another story be told.