Three and a half stars would be more accurate. There's a lot of fascinating worldbuilding here, presented very much in the "sink or swim" style where you're simply dropped into the world and must figure it out as you go. Neat stuff, but the pacing felt a little off...there's a lot of time spent setting the board, only to have the endgame sprung upon you faster than you expect. I'm not sure if I'd have preferred less setup (at the possible expense of less comprehension of the world) or more climax/denouement (which might remove some of the power of the "aha!" moment at the end), but it felt somewhat off-balance.