Unlike many romance dramas that let their protagonists meet early in the movie, Book of Love makes them meet toward the end.
"The tale is not only about love but also about the destinations, family connections and the struggles of elderly Chinese immigrants to find cultural familiarity abroad," Xue tells China Daily.
The director recently appeared for an event to promote the film at Beijing's Tsinghua University.
She describes the film as a "heartwarming" story that revolves around the question of how to maintain emotional ties in today's fast-paced societies.
In addition to the couple's somewhat old-school platonic love, the film interweaves dialogues with many ancient Chinese poems, such as the popular lines written by Tang Dynasty (AD 618-907) poets Li Bai and Wang Changling.
Most of the poem-studded lines are spoken by an old Chinese immigrant in Los Angeles.
Xue explains that the poems are a key measure for the elderly Chinese immigrants to protect their cultural roots.
"Ancient Chinese poems represent the most typical part of Chinese culture. I hope the dialogues don't make young audiences feel alienated, because that's not the intention," she says.
Xue also says the correspondence in the film is to remind viewers of the beauty of handwritten letters, rare items in the era of the internet.
"If you write, you will come up with some beautiful lines. You can hardly find those from just talking or sending messages on phone apps or over social media," she adds.
Xue hopes the film will also help revive moviegoers' interest in offline reading. She says the Chinese version of 84, Charing Cross Road is likely to be reprinted in the thousands as part of the film's promotion.
Alongside Macao and Los Angeles, the film has scenes in London, Las Vegas, Vancouver, Hong Kong, Beijing and Southwest China's Sichuan province.
Xue says a replica of the London bookstore depicted in the book was built in Vancouver.
Book of Love is produced by Edko Films, a company that made China's all-time highest-grossing Monster Hunt, on a budget that's bigger than the 2013 movie's.
Other than Tang and Wu, the cast includes veteran Hong Kong actor Paul Chun and Chinese mainland actors Wang Zhiwen and Lu Yi.
