I'm currently re-reading these two old timers:
Sex and Zen & A Bullet in the Head: The Essential Guide to Hong Kong's Mind-bending Films
Hollywood East: Hong Kong Movies and the People Who Made Them
Both can be picked up ridiculously cheap used on Amazon and offer a wealth of information.
They also venture were most other books on HK films won't go.
Probably my favourite books on 80's/90's HK cinema.