David Tod Roy has done a wonderful job with this book. By rendering Jin Ping Mei into immaculately annotated English, he has made the book acessible not only to native English speakers, but to bilingual readers who may find the original's quirky colloquial Chinese difficult to follow.
Jin Ping Mei itself is a book with many layers. Often dismissed as nothing but a book of smut and bedroom acrobatics (yes, it is full of this dear readers), Roy argues that it is also a tale of Confucian morals, and the consequences of failing to heed them. The story focuses on the town of Qing He (Clear Lake), and the household of a well-to-do young merchant named Ximen Qing. The book is also a treasure trove of details regarding the clothing, festivals, traditions, etc. of late Ming dynasty China. (While the author set the book in the late Sung dynasty, I think this is but a fig leaf. It was the Ming dynasty he himself lived in that he was thinking of all the time).
Jin Ping Mei has something of a reputation in this corner of the world as an "erotic novel". Here, I would say it falls down. If you want smut, this is not the book for you.