Below are the best books we could find on Non-Duality.

The concept of non-duality is based on experiencing the world as not separate from oneself, where awareness transcends the dualistic concept of “I-other” and other dichotomies such as good and bad or right and wrong. It involves a complete suspension of personal judgment on “outside” entities because those entities are seen as completely one with the individual, so there is no longer such thing as observer and observed. A non-dual existence involves pure experience, with no divisions between the subject and object. Non-dual consciousness has been described within several spiritual traditions, including Hinduism, Buddhism, Sufism, and Christianity, as well as within neo-Platonic philosophy. The most common ways to experience non-dual consciousness are through meditation and contemplation of certain “pointing out” instructions, to help reveal an awareness of what is already there to begin with.