Shri. Sharma, in the introduction of the book, begins by stating that both philosophy and religion try to pose the fundamental question "What is real?"
The book begins with how the Hindus wanted to attain liberation in this world itself (jivanmukti) rather than, postponing it to a later time, either death or on the judgement day, as in Christianity and Islam.
The introduction explains the six systems of Indian philosophy nicely. My notes from Dasgupta's book on the same subject is here. Both agree nearly. Sharma orders the astika systems as (Nyaya, Vaiseshika), (Samkhya, Yoga) and (Mimamsa, Vedanta). The first pair, he notes, are closer to naastika systems, while the second pair accept Vedas a-posteriori. Sharma also notes that Mimamsa and Vedanta take a very close approach to how the Vedas are interpreted, i.e., both the schools base themselves on the Vedas. They are based on the "anta" part of the Vedas. Though, as in some other religions, Hindus accept that the Vedas were received, Hindus also recognize the limitlessness or infinity of Vedas. This also means that Hindus attribute no specific time or place or persons -- either cosmic or human -- for the "receiving process" of the Vedas.
Also he explains the four parts of each Veda as (i) Mantras or Samhitas: the hymns in praise of gods, (ii) Brahmanas: the prose explanations of the ritual use of these hymns (iii) Aranyakas: reflections on the significance of the ritual and (iv) Upanishads: Secret texts meant to communicate the highest mysteries which go beyond ritual into the realm of spiritual knowledge.
In the explanation of the first Mahavakya Aham Brahma Asmi (I am Brahman), Sharma nicely notes that though everything "is" Brahman, the way in which Maya (or the universe) "is" Brahman is not the same as Atma "is" the same as Brahman.
The conclusions has the following translation of the famous verse on the main tenet of Advaita:
The non-duality of the Brahman,
The non-reality of the world
and the non-difference of the Atman from the Brahman
These constitute the teachings of Advaita
Considering that one of Mr. Sharma's books is dedicated to Eliot Deutsch, It is surprising that the book does not to cite Deutsch's book.
On another note, Arvind Sharma's experiential approach to Advaita seems to be unique and special. This is partly because, one of the primary questions of Advaita is "What is Real?". This question has to arise in the seeker's mind, after he feels that some of his experiences are not real!
A reader on the advaitin mailing list had recommended strongly, the book "The Rope and the Snake" by him. This is the Amazon link.