Sometimes I find things that are Buddhist in nature but maybe not specifically Nichiren Buddhist... Yet it correlates to Buddhist thought and seems to offer a deeper truth and understanding to my Practice of Nichiren Buddhism and Life.
This is one of them: The Power of Now by Eckhart Tolle
ps: You may not understand everything in the book but just keep reading it (don't quit!) Then read it again 2 years later. And then again 2 years after that. You will be amazed at your personal growth, your understanding of Life and how much your life has changed over the years!