In the movie The Equalizer (2014), there is the following conversation:

Teri: What's your book about?

Robert McCall: It's about a guy who is a knight in shining armor, except he lives in a world where knights don't exist anymore.

Does anyone know what the book is that Denzel Washington (Robert McCall) is talking about?

Is it even about a real book or is this just a line for the movie?

Notes: Also in the movie, he makes a reference to Moby Dick which leads me to believe that this line is also about a real book.