Book on the shelf

He's actually referring to a Bible that was given to him as a gift.

I wasn't positive, but I thought it looked like FLOWERS FOR ALGERNON

It's been a long while since I read it but the plots of the book and movie seem quite aligned

Charlie falls in love with his former teacher, Miss Kinnian, but as his intelligence increases, he surpasses her intellectually, and they become unable to relate to each other. He also realizes that his co-workers at the factory, whom he thought were his friends, only liked him to be around so that they could make fun of him. His new intelligence scares his co-workers, and they start a petition to have him fired, but when Charlie finds out about the petition, he quits. As Charlie's intelligence peaks, Algernon's suddenly declines—he loses his increased intelligence and mental age, and dies shortly afterward, to be buried in a cheese box in the backyard of the lab where Charlie was tested. Charlie discovers that his intelligence increase is also only temporary. He starts to experiment to find out the cause of the flaw in the experiment, which he calls the "Algernon-Gordon Effect". Just when he finishes his experiments, his intelligence begins to regress to its state prior to the operation. Charlie is aware of, and pained by what is happening to him as he loses his knowledge and his ability to read and write. He tries to get his old job as a janitor back, and tries to revert to normal, but he cannot stand the pity from his co-workers, landlady, and Ms. Kinnian. Charlie states he plans to "go away" from New York and move to a new place. His last wish is that someone put flowers on Algernon's grave.