The real meaning

I just read the first two pages of the book over on amazon.com to familiarize myself with the context the quote came from.

It sounds to me like he is remembering Phuong as she used to be at another time in their lives. It sounds like he is using metaphors to symbolize his past sexual attraction and experiences with Phuong at another time in their lives, that she has since changed.

Hi Dekka and welcome to a2k.

I shut my eyes and she was again the same as she used to be: she was the hiss of steam, the clink of a cup, she was a certain hour of the night and the promise of rest.

I'm not sure whether you want specifics. Metaphors are open to interpretation. For example, the hiss of steam may represent heat. The clink of a cup may remind him of a gentle bell-like sound--her laughter, perhaps. A certain hour of the night may refer to how one feels at a particular time, or it may refer to sex. The promise of rest may also refer to sex or may suggest that she was someone who could help him relax, feel comforted, or something similar.

I hope your question is answered.

Thank you Butrflynet and Roberta. Your comments are very helpful. It is nice to have support from you guys. I guess I can have a bit of my own imagination in interpreting them.

Are these expressions (metaphors) established ones or the author invented them himself?

So far as I know, they are the author's own inventions. And, IMO, good ones, at that.