As an esoteric eclectic, I have devoted the past four decades to both the study and practice of the foremost spiritual traditions--Theravada, Zen, and Tibetan Buddhism; Hindu Raja Yoga, Advaita Vedanta, and Kashmir Shaivism; Daism (the teachings of Adi Da); and Christian Hermeticism, and in this time I have never encountered a spiritual book better than Talks with Sri Ramana Maharshi. If I could give it six stars, I would. The book is a collection of enlightening talks between Ramana and numerous individuals representing the entire spectrum of spiritual development. The talks, which took place between 1935 and 1939, include conversations with such notables as Paramahansa Yogananda and W.Y Evans-Wentz, author of The Tibetan Book of the Dead.
I am well aware of the progression of Advaita Vedanta gurus since Ramana, and I've read the books by Sri Nisargadatta Maharaj, Ramesh Balsekar, Papaji, Jean Klein, Andrew Cohen, Gangaji, Adyashanti, and many of the others who have come after Ramana. As a spiritual teacher, when I'm asked to compare these "gurus" to Ramana, I usually become like Sparky Anderson, who managed the Big Red Machine in the 1970s. When Sparky was asked to compare other catchers to the Reds' catcher Johnny Bench, his reply was: "I don't want to embarrass anyone." Sometimes someone will insist that Sri Nisargadatta's I Am That is better than Talks with Sri Ramana Maharshi. All I can do at that point is be like Jesus and "forgive them, for they know not what they say." Nisargadatta, unlike Ramana, did not awaken as the Heart and radiate Hridaya (or Cit) Shakti, and he didn't talk about Amrita Nadi, the radiant force-current between the Hridaya, or Heart-center (just to the right of the center chest, and distinct from the anahata, or heart, chakra).
What separates Ramana from the other Advaita Vedanta gurus is the breadth and depth of his teachings. For example, I read Adyashanti's book Emptiness Dancing many years ago, and in it, he said that he said he had a kundalini experience when he practiced Zen (before later becoming an Advaita Vedanta-type guru). But he never said another thing about kundalini in the book: how it relates to the enlightenment process and Self-realization. By contrast, Ramana says Kundalini is another name for the Self. In other words, for Ramana, the Self is not just static Consciousness, but also dynamic Energy; in other words, Siva-Shakti. Although Ramana is considered an Advaita Vedanta guru, his teachings transcend the tradition.
None of the other Advaita Vedanta gurus I mentioned explicitly taught or teach Ramana's method of Self-enquiry ("locating" the transcendental `I,' or Self, by undermining the false `I,' or ego-self) Self-enquiry is the most powerful and direct method to realize the Self (in, and eventually as, the Heart)--and it is beyond my comprehension how any true Advaita Vedanta guru could not teach it. Along with Dzogchen-type contemplation, it is what I teach my students.
If you decide to buy Talks with Sri Ramana Maharshi, do NOT buy the Inner Directions publication, which has been shamelessly edited (and grossly de-esotericized). Instead, get the Sri Ramanasramam one, by Munagala Venkataraman, available at Amazon.com (or Google Arunachala Ashrama and get a higher-quality hard-cover version). If you decide to start out with an introductory Ramana book, get the excellent compendium Be As You Are: The Teachings of Sri Ramana Maharshi, by David Godman.