I see this book is on Amazon pre-order. Have a couple of Safari Ltd Chinese dragons that I've been looking for a suitable game to use. I hope it has dragons (!)
Terrain? HK does have its modern shopping malls, glass highrises, as well as parks and green space. Also island fishing villages, at least one monastery, a large shipping port, casinos (in Macau)....
I'd guess most people would have in mind a "hard boiled" street look. Plain concrete exteriors, exposed air conditioners, laundry hanging from windows--a lot of neon of course. Don't forget the occasional McDonalds, KFC, or 7-11. Taxis, double-decked buses. You could look at Google Images for ideas: "Kowloon walled city", "Chunking Mansion", "Nathan Road", "Mongkok", etc.