Can we climb Mount Everest just by reading books? To climb a mountain and that too the highest mountain in the world we need to be proficient in mountaineering. Similarly to indulge in spirituality to reach state of self realization we have to master the delicate art of contemplation (chintan) so that we could continue with our inner journey all the time.
Even though many books are available in the open market relating to self realization but all these were authored by people who knew nothing about self realization. Mahavira (24th Tirthankara of Jainism, preceptor) always said; do not preach anything unless you become an enlightened one.
Self realization can never be understood through books. Everything in field of self realization has to be realized from within by travelling the inner journey towards our soul atman existing in heart. Self realization is a process of cleansing our soul atman by indulging in contemplation (chintan). There was never a shortcut path to self realization.
Self realization, God realization, enlightenment all meant the same.
However to reach state of self realization, to indulge in spirituality the sermon of Bhagavad Gita by Lord Krishna comes to our rescue. In the entire history of mankind ever since Lord Krishna gave sermon of Bhagavad Gita, every single seeker succeeded in reaching state of self realization only by indulgence in teachings contained in Bhagavad Gita.
Authentic commentaries on Bhagavad Gita containing original text of 700 shlokas verses in Sanskrit followed with Hindi and also English transliteration are available for mere $1-$3 from Gita press, Gorakhpur, India. Gita press has bookshops in many major cities of India and also online presence. Commentaries on Bhagavad Gita available with Gita press are the only authentic commentaries available world over.
Commentary on Bhagavad Gita by Adi Shankaracharya is also available with Gita press. As Gita press has many editions of commentaries including translations, it is advisable to visit the bookshops in person and select what suits our appetite, our pattern of thinking.