Academic mystery/fantasy-maybe-SF/romance told in two sets of letters. Surprisingly loved the epistolary format and the way we got gradual hints and reveals about the world, the characters, and what happened in the past. **Loved** that the "in the present" MCs built up such a lovely relationship that did not become a romance or anything like it -- deep platonic friendship as an end goal from two people in loving relationships felt like such a win. The world building was also fun: the Anne McCaffrey style "is it SF or fantasy" conceit and the queernormative world were just fun. A good time; will read the next one!