-disclaimer: I have not played this yet-
Style: 5/5. It's gorgeous. Colourful, filled with art, with nary an inch of wasted space.
Substance: 5/5. There's so much of it! 15 rooms worth of detailed encounters, full NPC statblocks, traits, rewards, collectibles and an frightening mechanic for running out of air. Without playing it I can't think of anything to add; it's quite comprehensive on first read.