Sage Sankara does not believe in the book, he denies the authority of any book over any other book.+

All the philosophies are mental fabrication based on a dualistic worldview.  There has never been a single doctrine by which one could reveal the truth hidden by the universe other than Sage Sankara's Advaitic wisdom. 

Sage Sankara does not believe in the book. He denies the authority of any book over any other book. He denies emphatically any one book contains all the truths about God, Soul, the ultimate reality, or Brahman or God in truth.

Advaitic wisdom is independent of religion.  Sage Sankara himself the Saguna Brahman or a personal God is only a part of the phenomenal (if not illusory) world and the Nirguna Brahman is the only reality and has nothing to do with religion.  

It is very difficult to bifurcate the pearls of the hidden wisdom of Sage Sankara from the contamination of theistic Advaita and Advaita Vedanta.   

Sage Sankara's wisdom (Advaita) ~ Without a Parallel.  Sage Sankara's wisdom is lofty, sublime, and unique. It is highly interesting, inspiring, and elevating. No other wisdom can stand before it in boldness, depth, and subtle thinking.  Sage Sankara’s wisdom is complete and perfect.

Sage Sankara was a mighty, marvelous genius. He was a profound thinker of the first rank. He was a sage of the highest realization. His wisdom has brought solace, peace, and illumination to countless persons in the world. The Western thinkers bow their heads at the lotus-feet of Sage Sankara. His wisdom has soothed the sorrows and afflictions of the most forlorn persons and brought hope, joy, wisdom, perfection, freedom, and calmness to many. His wisdom commands the admiration of the whole world.

Sage Sankara pokes fun at ascetics and points out that all their austerities do not cause desires to go (Altar Flowers" Page 205, v.2 P.207 v.4)

The Brahma Sutras together with Sage Sankara's commentary thereon do not contain the higher wisdom. They are intended for those who are incapable of thinking rationally.

Sage Sankara's commentary on the Brahma Sutras is not on a philosophical basis, but on an orthodox and mystic basis, with an appeal to the Vedas as a final authority.

In Brahma Sutra Sage Sankara takes the position that there is another entity outside us, i.e. the wall really exists separately from the mind. This was because Sage  Sankara explains in Manduka that those who study the Sutras are orthodox minds, intellectual children, hence his popular viewpoint to assist them. These people are afraid to go deeper because it means being heroic enough to refuse to accept Sruti, and God's authority, in case they mean punishment by God.  A Gnani says the scriptures for children, but wise seekers will think rationally.

In Brahma Sutras Sage Sankara takes for granted, assumes that a world was created: He there mixes dogmatic theology with philosophy.

That God created the world is an absolute lie, nevertheless one will find Sage  Sankara (in his commentary on Vedanta Sutras) clearly says this! He has to adapt his teachings to his audience, reserving the highest for philosophical minds.

The text of Brahma Sutras is based on religion, dogmatism, but in the commentary Sage Sankara cleverly introduced some philosophy. If it is objected that a number of Upanishads are equally dogmatic because they also begin by assuming Brahman, only a few Upanishads do not but prove Brahman at the end of a train of proof.

Scholars' translation of Brahma Sutras in Sacred Books of East must be read cautiously as he has not understood its highest sense, e.g. for Advaita, they wrongly put "Unity" instead of “Non-duality."

Sage Sankara gave religion and scholasticism and yoga no less than philosophy, to the seeking world. He was great enough to be able to do so. His commentary on Mandukya is pure philosophy, but many of his other books are presented from a religious standpoint to help those who cannot rise up to philosophy.

Advatic Orthodoxy is the home of mysticism and deification that is why they are not very keen on rational truth.

Sage Sankara is a Jagaduru to the religious followers and he is a Brahma Gnani to the seeking world. 

Remember:~

There are hundreds of commentaries from different authors on the Bhagavad Gita. Each one goes on spinning yarns imagining as he likes what the meaning may be.

Bhagavad Gita has been interpreted in a thousand ways, according to the author’s capacity to understand the test of all these is the reason. Only a few understood Bhagavad Gita.

Bhagavad Gita is a hodgepodge containing everything; hence it suits the populace because there is something in it for every type of mindset. It is difficult to find any tradition whose voice is not found in the Gita. It is difficult to find anyone who does not take solace from the Bhagavad Gita. But for such people, the Advaitic path will prove very difficult.

Once you are Soul centric you will know what Bhagavad Gita and other scriptures really meant, you will see that there is only one possible interpretation, irrespective of diverse opinion or imagination.

Bhagavad Gita does not contain higher wisdom. Bhagavad Gita is intended for those who are incapable of thinking rationally.

Bhagavad Gita 2:46:~  "A man of true knowledge who has attained enlightenment, has the same use for all the scriptures as one has for a small reservoir of water in a place flooded on all sides."

People love Bhagavad Gita because it is very easy to extract one's own meaning from it. Reading Bhagavad Gita a religious believer extracts something of which he can make a belief because Bhagavad Gita speaks on bhakti, devotion. The karma yogi extracts his belief because Krishna has spoken on karma yoga, the Yoga of action. The believer in knowledge finds what he wants because Bhagavad Gita has spoken on knowledge as well. Somewhere Krishna calls bhakti the ultimate, somewhere else he calls knowledge the ultimate, again elsewhere he calls karma yoga the ultimate.

Lord Krishna taught the Karma and Bhakti yogis their own paths only to lead them up to the Gnana yoga path, which is the highest and the real object of his teaching.

Lord Krishna confesses that the oldest wisdom of India (our true Advaita philosophy) has been lost: people misinterpret and falsify it today as they did then. It is not yoga but the philosophic truth. But nobody knows it. The teachers of philosophy and leaders of mysticism or religion do not want to inquire into truth and have no time for it. (Gita ~ Chap ~IV~ v.2)

Why is the word Yoga used in so many different senses in the Gita? Because there are grades and the highest demands concentrated brains, not sitting mindless and imagining you are seeing God.

In Gita Chap.IV where Lord Krishna says: ~ “This yoga has been lost for ages" the word yoga refers to Gnana yoga, not other yogas: the force of the word this is to point this out.

Lord Krishna describes some of the other yogas but devotes this chapter separately to Gnana Yoga. So one sees even in those ancient days people did not care for Advaita; they used religion; hence Gnana got lost. That is why Krishna calls it "the supreme secret." Krishna points out that yoga must-see "Brahman in action."

Gita Chap.IV:~ “He who achieves perfection in Yoga finds the Self in time." This means that after his yoga is finished, he begins the inquiry into ultimate truth, and in due course, this inquiry produces the realization of the universal spirit as the result.

Understanding what is God is not so easy. Religious people can only imagine God based on their beliefs.

That is why Lord Krishna Says Ch ~V: ~ “Those who know the Self in truth.". The last two words (tattvataha) are usually ignored by pundits, but they make all the difference between the ordinary concept of God and the ruth about God.

No duality, no differentiation. Only Atman exists.

Remember:~

Bhagavad Gita: ~ ‘All those whose intelligence has been stolen by material desires, they worship many God s. (7- Verse -20)

Only the path of wisdom leads the seeker of truth on his journey to the ultimate realization of the true nature of the Universal Essence, which is the Soul. The Soul is present in the form of consciousness.

Bhagavad Gita: 7:19:~"Such a man who has attained true knowledge, the knowledge of Self, knowledge of Atman, worships ‘Self’ as~ Atman (God) alone exists~ everything is Atman there exists nothing except Atman. Such a man is extremely rare"

The Bhagavad Gita:~Brahmano hi pratisthaham ~ Brahman (God) is considered the all-pervading consciousness, which is the basis of all the animate and inanimate entities and material. (14.27).

When Bhagavad Gita says, God is considered the all-pervading consciousness which is the basis of all the animate and inanimate entities and material then nothing has to be accepted as God other than consciousness.

Lord Krishna Says Ch ~V:~ “Those who know me in truth.". The last two words (tattvataha) are usually ignored by pundits, but they make all the difference between the ordinary concept of God and the truth about God. 

The dualistic worship of "God” is only for the ignorant populace. The God in truth is only Atman, the innermost Self. In reality, there is no duality, no differentiation. Only Atman exists.

Remember:~

Bhagavad Gita: 5: 19:~ "Those who have achieved the true knowledge i.e. the 'Self-Knowledge' or the 'knowledge of Atman' and see no difference, are free from conflicting dualities have merged in Brahman.

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Bhagavad Gita: 5: 20:~ "One who does not get excited out of happiness on getting good and does not get depressed on getting bad is situated in Brahman i.e. is merged in Brahman.

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Bhagavad Gita: 6: 9:~  "The one who has equal the vision for a Selfless do-gooder, a friend, a foe, an unbiased, a well-wisher, a depressed and jealous man, relatives, a righteous and a sinner is the best (as he sees no duality and differentiation but sees everything as Ātman)"

Bhagavad Gita: 6: 32:~ “.....as one seeks and treats oneSelf with equal vision, the same way one who has an equal vision for good and evil, for everybody is the best of all".

Bhagvad Gita: 6: 8:~ "For whom soil, a pebble, and gold are alike, he is merged in Brahman.

Bhagavad-Gita Gita: 7: 27:~ ".....people are getting entangled in the primordial ignorance (Avidya) of the conflicting dualities like good and evil, happiness and sorrow caused due to attachments, desires, and hatred....."

Bhagavad Gita: 6: 28:~ “.....who have cut-off conflicting dualities (like good and evil)is determinedly in my service. ...."

Bhagavad Gita: 7: 19:~ "Such a man who has attained true knowledge, the knowledge of Self, the knowledge of Atman, in the last birth in the series of many births worships Me as~ Atman alone exists~ everything is Atman, there exists nothing except Atman. Such a man is extremely rare."

A Gnani sees no duality and differentiation but sees everything as Ātman. The knowledge of both matter and spirit is True knowledge. The true knowledge is Self-knowledge or Brahma Gnana or Atma Gnana. : ~ Santthosh Kumaar