A complete practical Guide, the SGGS is the Source of Wisdom (Giaan) pertaining to the quest of Truth, and provides all that's needed to raise consciousness to the highest dimension: the plane of the truthful living (the Gurmukh Lifestyle).
Free of dogmas, the Gurbani has a simple message: there is One, All-pervading Reality. We are That. The purpose of human life is to understand this Truth through self-purification and self-observation while alive - not after death, but here and now. Only then we can take off from levels of Bikaars (ego's passions, negativity, etc.) into heights of our True Nature (Joti-Svaroopa or godly status), spontaneity (Sahaj), Perfection (Pooran Pada), etc.
To this end, the SGGS urges us to: lead a Divine Life (the Gurmukh Lifestyle); make truthfulness the core of daily life; make a dedicated life of selfless service (Sevaa) to all beings the prayer; make Wisdom, humility and contentment the temple within; make the practice of selfless love and compassion for all the devotion and the noblest conduct; make meditation (Simran) the rosary enshrined in the heart; realize Oneness with the Universal Spirit, within; recognize the Sameness in all; become Jeevanmukta (Living Enlightened or Liberated) and experience Bliss (Anand), Peace, Harmony, Joy; etc., within, while alive.
Otherwise, what's the use of reasoning, intellectuality, reading scriptures and listening to their recitations? And what's the use of talking about religion, spirituality, and Truth if not lived?
It is repeatedly indicated in the SGGS that there are only two different groups of people living together on earth: the Gurmukhs (the followers of Truth and truthful living, etc.) and the Manmukhs (the deniers of Truth and truthful living, etc.). The SGGS asks us to become the Gurmukhs.