Technically it's a shipping fic, but also features plenty of adventuring and could easily double as Golden Sun
3.5 (not 4 because it doesn't feature Alex, Sheba, Amiti, Eoleo, and Himi). The story employs a copious amount of self awareness and game mechanics (such as the Warriors Of Vale frequently talking about how absurdly powerful they are compared to others, and lampshade hanging in regards to having to solve puzzles), along with its fair share of twists and turns. Also prominent are the author's notes sections at the end of each chapter, where jolly answers reviewer questions and gives insights into his thinking process (and tells you when he decides to go back and rewrite chapters for improvement). Finally, characters who never had much development in the games (ie Mia and Rief) are given personalities here, and it's definitely for the better.