The movie itself was based on a fictional story inspired by the real Titanic disaster. While there have been many books written about the Titanic disaster, there is no known novel specifically focusing on a fictional love story like that portrayed in the movie.
However, there are many books that delve into the historical aspects of the Titanic disaster and the lives of those involved. Some of these might offer inspiration or a basis for imagining a fictional story about love aboard the Titanic.