40 Forty Rules of Life by Maulana Jalaluddin Rumi

It seems like you might be referring to "The Forty Rules of Love" by Elif Shafak, which is inspired by the teachings of Maulana Jalaluddin Rumi. However, if you are looking for a book titled "40 Rules of Life" by Rumi, there isn't a widely recognized book by that name.

Would you like a description of "The Forty Rules of Love", or are you looking for a general summary of Rumi’s life principles?