Guru Nanak & Sikhi
Guru Nanak (1469–1538) (also called Baba Nanak or Nanak Shah) is one of the greatest religious innovators of all time. He was a Prophet of God.
There are 11 Gurus of Sikhism including 10 Nanaks ("They shared the one light", Ang 966) and the Shri Guru Granth Sahib (SGGS) which is our eternal living Guru.
Gurbani Vichar is a detailed review of the Sikh Holy Book, the SGGS from a spiritual perspective. It incorporates both Sufi and Hindu thinking and also covers Sikh history.