I for one am not into Gamebooks, to be honest I don't even like reading Books, but the trailer in this game just made my jaw drop, it's pretty incredible. The game is called Karyl's Grimoire and unlike most stories, your choices affect how the story unfolds and your decisions have a direct impact on the story’s events, the journey your hero takes and the conclusion he ultimately faces.
AsKaryl's Grimoire - Gamebook with an amazing trailer (iOS)