I'm not sure what book you're referring to, but if I take your question literally, "Melody Nelson" was a fictional muse for Serge. I really enjoy this albums "mood", if you put the context into the time period it came out, it plays into the love affair, open minded-ness that Americans had with French culture in the early 70's. Take movies like The Last Tango in Paris, same story, same "icky-ness"............whole other level btw, but Serge's album fit right into the times.
The mood of the musicality, mood and feel of the album are what works for me. You could listen to this not understanding a word of what's said, or the lyrics and still enjoy it.