Gayatri mantra is a Vedic prayer. It is a universal prayer that can be used by any person, belonging to any country, irrespective of race, religion, or sex. This book includes the symbolism of Om and the Gayatri, the scriptural references where they are mentioned, as well a detailed instruction on how to perform the Sandhya rituals. Text for the rituals is in Sanskrit with transliteration, and English translation.
The book one must read to learn natural sciences is the book of nature. The book from which to learn religion is your own mind and heart.
-Swami Vivekananda